It was somewhere deep in the Bloodroot Valley that I realized Richmond Creek must be the longest stream in New York City.

I had been hiking for three days, tracking out its convoluted route through overgrown backyards and rocky ravines, scrambling up waterfalls, over weirs, and past century-old ruins. Miles into an unnamed forest, far from the nearest road and accompanied only by a few dozen deer, the origins of the creek began to materialize.

Stretching over five miles from its furthest tributaries in the Staten Island Greenbelt to its mouth in Fresh Kills, Richmond Creek flows through many layers of hidden history. Its waters pass by toxic landfills and old mill remnants, a historic town museum, a manmade mountain of rubble, a vast Boy Scout camp, and an abandoned tuberculosis hospital.

Along its entire course, the creek is a fascinating blend of natural and engineered landscapes, simultaneously operating as a stormwater drainage system and a wildlife sanctuary for several rare aquatic species. Staten Island’s only population of northern two-lined salamander live along its banks, while its waters host New York City’s only population of blacknose dace and the first beavers to appear in the city in over 100 years.

Wandering through Richmond Creek’s teeming ecosystems today, it is surprising to consider that just 20 years ago, this was one of New York City’s most contaminated waterways, polluted by raw sewage from backed-up septic systems.

“Bacterially speaking, it was just horrific,” says Robert Brauman, the construction project manager for the Staten Island Bluebelt, which began working to improve the creek in the 1990s. “Parts of it were almost like an open sewer, and you could smell the urine.”

Although the scars from centuries of human interference are still readily apparent all along Richmond Creek, it has now been transformed into one of the most pristine waterways in New York City, thanks in part to the Department of Environmental Protection’s (DEP) unique Bluebelt program, which brought a new sewage system to the area. Similar water management systems now encompass most of the creeks and waterways around Staten Island, but it all began with Richmond Creek, the original Bluebelt. “It really is a unique stream on Staten Island,” said Brauman. “It is the cleanest I know of, for sure.”

The lingering aftereffects of unchecked human pollution in the Richmond Creek watershed are most readily apparent along the creek’s western half, where it flows down from the old Mill Pond in Historic Richmond Town to its mouth at Fresh Kills. Here, the vast salt marshes that once lined the creek’s terminus at the Arthur Kill were long ago filled in to create the unnatural hills of the Fresh Kills Landfill and Brookfield Landfill. Although these city dumps have now been closed down, capped and remediated, and will soon become public parks, the water around them remains contaminated by toxic leakage.

Further inland, in an area just downstream from Richmond Town, a collection of even older industrial remnants are buried in the overgrowth. Along Old Mill Road, a man-made wilderness hides evidence of settlements dating back several centuries to the indigenous Lenape people.

Although the scars from human interference are still readily apparent, Richmond Creek has been transformed into one of the most pristine waterways in NYC.

Recently, a hike through these historic ruins was led by the Protectors of Pine Oak Woods, a preservation and conservation group which initiated an extensive reforestation project here 40 years earlier. This was the group’s first official visit to some of these ruins since the 1970s.

Ambling along a tangled system of demapped streets, bike trails and deer runs, the Protectors visited the remains of several 100-year-old homesteads, their crumbling fireplaces and filled-in wells covered by vines. “You might find a button, buckle or musket shot. They are artifacts from the British era,” says Ray Matarazzo, the hike leader and a retired science curator for the Staten Island Museum. “Other people have found arrowheads and Native American artifacts.”

Also hidden in these abandoned settlements were reminders of a long history of landscape engineering along Richmond Creek. “Staten Island had about 11 mills on it, and three were here,” says Matarazzo, pointing out several large earthen berms and holding ponds that were concealed in the dense woodlands, where the creek’s tributaries had once been re-routed into milling operations. The last remaining mill stood in the creek’s salt marsh until the 1920s, but extensive artifacts from its other mill complexes still exist today.

Over the centuries, this section of Richmond Creek was slowly filled in by runoff and silt from mills, farms, and household waste. “This creek was once big enough for a warship to sail up,” says Matarazzo, who has been exploring the waterway since his childhood, camping along its shores and canoeing down its main branch. “Even 50 years back, it wasn’t as silted in, so the waterways would have been more navigable for small craft. But today, at low tide, it’s pretty mudded up. You get caught in this creek in the low tide now and you’ll be stuck in silt for 12 hours.”

In the creek’s middle section, where the engineered landscape of the Richmond Creek Bluebelt routes its waters through the backyards of Richmondtown, the DEP first began addressing the problems of pollution and silt back in 1996. “Due to all the development upstream, the creek was full of sediment,” says Brauman. “That pond was about six or seven feet deep originally. It was probably only four inches deep when we got there.”

Today, the pond has been restored to its original mill-era depth, with silt and sewage dredged out and a new fish ladder built up over its weir, allowing American eel to return upstream on their 2,000 mile journey from the Sargasso Sea. Upstream, the Bluebelt has created an extensive system of storm drains, culverts, stilling basins, wetlands, and detention ponds, which have helped alleviate the chronic flooding which once plagued the residents of Richmondtown. “That’s the low point in the entire watershed,” explains Brauman. “That area, before the Bluebelt, routinely flooded. It was impassable.”

The largest feature of the Bluebelt is located upstream from this residential area, near the head of the Egbertville Ravine. Here, at the junction of several of the creek’s major tributaries, an enormous detention basin has been built to capture and retain its overflowing waters. “That site is the one that really relieves the flooding downstream,” explains Brauman. “When it rains, it can store five feet of water before it overflows. In a big rain, it’s like Niagara. You can hear it from a quarter mile away, going over that wall.”

The final section of Richmond Creek, beyond the Bluebelt, is its most wild, as its tributaries flow downhill through the forests and wetlands of the Staten Island Greenbelt, a 3,000-acre parkland. An extensive system of hiking trails has been created here, but the creek wanders along on its own route, and any attempt to follow its course quickly becomes an off-road adventure through thickets of brambles. With numerous branches spread out over several miles, many of the creek’s sources remain hidden in forests and glens.

The longest branch of Richmond Creek originates near Todt Hill, where it meanders down from “the highest natural point on the Eastern Seaboard south of Maine” before passing through the 143-acre William H. Pouch Scout Camp, the ruins of the Seaview Hospital campus, and the isolated beauty of the Blood Root Valley. In greener weather, these sections of Richmond Creek would be impossible to navigate, but in autumn, most of the waterway can be tracked, although deer outnumber humans in this unspoiled wilderness.

Unlike the Bronx River and Hutchinson River, which certainly have longer flows, the headwaters of Richmond Creek and its many tributary branches are entirely contained within Staten Island, making this the longest and most extensive aboveground waterway contained within New York City. Mapping out its entire watershed will take many more days of wandering.

Standing above the creek at Richmond Avenue, a mile inland from its mouth, it is hard to imagine that its origins can be found in small trickles four miles away. At high tide, the creek here is a broad, flat expanse of brackish water, over 300 feet across.

The shores of the creek in this area are largely inaccessible, blocked off by landfills and dense fields of invasive phragmites. An overgrown access road on the creek’s northern bank is one of the only public access points into the creek’s former salt marsh.

The road terminates at creek’s edge, where a cluster of DEP manholes cover an overflow pipe extends into its waters. On the opposite bank sits the capped Brookfield Landfill, a 272-acre toxic waste dump.

Further east along the shoreline, abandoned cars and other signs of human life are hidden in the woods. Several old roads once cut through these forested areas on the north side of Richmond Creek, but most have been demapped and returned to nature.

A system of narrow foot trails follows within sight of the creek’s marshland, winding through several stands of native pitch pine and river birch that were planted by the Protectors of Pine Oak Woods in the 1970s. This area is part of the Staten Island Greenbelt.

A recent hike lead by the Protectors visited the ruins of the three old mills that once lined Richmond Creek and its tributaries. “This is the time of year to do this walk, because when it’s all greened in you can’t see any of this,” says Matarazzo, the leader of the hike. “This mill hike hasn’t been done since the 1970s. It was too overgrown and inaccessible.”

At the ruins of the Ketchum’s Mill complex, old walls and watercourses from the 1800s are still visible. “They probably had a dock on the creek, but they were relying more on the Old Mill Road,” says Matarazzo.

Ketchum’s Mill was powered by a diversion of one of Richmond Creek’s numerous tributaries, Ketchum's Mill Pond Brook. The brook flows through a forested area, from the LaTourette Park & Golf Course to the north of Richmond Creek.

On a ridge above Richmond Creek, a smaller tributary bubbles to the surface at Lord Howe’s Spring. Also known as Hessian Spring, the fresh water here is linked to Revolutionary War history. “This was a water source for the British occupation,” says Matarazzo. “When we were kids, we used to fill our canteens here.”

Downhill from the spring, Old Mill Road itself was once accessible for cars, but has now been turned into a Greenbelt hiking path. “When I was a kid, the original Old Mill Road was still open,” notes Matarazzo. “But in the mid-1980s, into the 1990s, Old Mill Road kind of grew in, because they gated it, and it was impossible to get down.”

The next appearance of Richmond Creek is near the start of Old Mill Road, on the grounds of the Church of St. Andrew, a NYC landmark dating back to 1872. The creek runs past an old cemetery here that dates back to the 1700s, before it flows into a silted-in, inaccessible salt marsh.

Upstream at Historic Richmond Town, the creek flows over a fish ladder at the old Mill Pond, which was dredged out as part of a Bluebelt restoration project. The historic homes near the Mill Pond date back to the 1700s and 1800s, and were relocated from other parts of Staten Island.

The pond and nearby wetlands are now home to at least two beavers. “That’s our first beavers in 100-something years in New York City,” notes Brauman. “It’s an interesting new critter for the area.”

Further upstream in the Bluebelt, the beavers have created a dam and lodge. Their reappearance was not planned by the DEP, but is a testament to the cleanliness of Richmond Creek. “They are doing what beavers do—they are backing up the water,” says Brauman. “It’s a great animal, but in an urban area, it’s hard.”

A rope swing hidden deep in a backyard wilderness along the Bluebelt, near two de-mapped streets. “People often wonder if the Bluebelt is meant to be a park, so they ask us why we are not mowing it or clearing it,” says Brauman. “It’s not supposed to be a manicured system.”

The constructed wetlands of the Bluebelt reach almost to the back door of some homes here. “The Bluebelt drains that whole area back there,” says Brauman.

A culvert at Aultman Avenue allows the creek to flow under streets that once regularly flooded. Prior to the Bluebelt, homes here relied on septic tanks, and were not linked into a city sewage system. Raw sewage would be piped directly into the watershed.

Upstream, Richmond Creek begins to flow through a much more rural landscape, although the creek bed throughout the Bluebelt was reinforced by the DEP. “The stream was very eroded from uncontrolled runoff,” says Brauman.

At Eleanor Street, the creek travels under a narrow bridge, marking the boundary between its currently inhabited banks and its wilder sections to the north. New housing developments around the watershed are still creating challenges for the creek.

As it courses through the Egbertville Ravine, Richmond Creek begins to resemble a natural woodlands stream, although even this is part of the Bluebelt system. “We design the Bluebelt to be as natural as possible, so we only use native trees and shrubs, and we let them go through natural succession and change with time,” says Brauman. “So we plant a lot of diversity to give it a good start and we let it do its thing.”

At the head of the ravine, several of the creek’s tributaries merge in the constructed Bluebelt landscape. One small branch flows in from the east, originating at Ohrbach Lake in Pouch Camp. Another flows in from the west, originating near Buck’s Hollow.

The creek’s major tributaries are gathered here in a large dammed basin, near the intersection of Rockland Avenue and Meisner Avenue. “At that point, that’s where three small tributaries come together to form Richmond Creek,” explains Brauman.

The longest of Richmond Creek’s tributaries flows into the basin from the north, from underneath Rockland Avenue. This road marks a border between the engineered landscape of the Bluebelt and the more natural landscape of the Greenbelt.

Across Rockland Avenue, as the creek flows through the thickets and brambles of the Greenbelt, it begins to resemble a more natural woodlands stream. “It has that upstate feel, because of its geology,” says Brauman. “It’s more of your classic stream, with a rocky, riffled bottom.”

A small trail through the Blood Root Valley is one of the only public access points to this stretch of Richmond Creek. The creek and trail both pass by Moses Mountain, a 200-foot high pile of rubble dumped into the woods by Robert Moses in the 1960s, from his failed plans to build a highway through the Greenbelt area.

The ruins of Seaview Hospital loom over this branch of the creek, which is also known as Dead Man’s Creek. This historic facility was a tuberculosis sanatorium built in the early 1900s. Most of its buildings have been abandoned for decades.

Access to Richmond Creek’s route is cut off by a chain link fence topped by barbed wire, perhaps once intended to keep hikers out of the old Seaview campus. In several sections, however, the fence has been crushed and broken by falling trees, or peeled back by curious visitors.

Richmond Creek branches yet again near the Seaview campus, with one of its tributaries flowing in from a forest wetlands in the Greenbelt, to the northwest.

This tributary emerges from a culvert hidden deep in the woods, surrounded by abandoned car parts. A constant trickle of water flows out of the pipe, and is collected in the nearby wetlands.

The longest branch of Richmond Creek, however, can be tracked even further to the northeast, as it crosses under Manor Road from Pouch Camp.

In Pouch Camp, the creek follows a meandering route through an archery range, crossed by several hiking trails, and passing by many of the camp’s 55 lean-tos and 20 tent sites. The creek branches off into several smaller tributaries in the camp, which flow in from the woodlands of Todt Hill.

Two branches of the creek meet in a ravine behind the camp’s jamboree field, with one tributary flowing down from the woodlands of the 75-acre Henry Kaufman Campground, near Todt Hill.

The waters of the second tributary are collected in this large wetlands area behind the Pouch Camp amphitheater, marked only by an abandoned drone.

Even in the chilly autumn weather, Pouch Camp is actively used by scouts. This campsite is located on the branch of Richmond Creek which descends from Ohrbach Lake, flowing back down towards the intersection of tributaries at Rockland Avenue.

Ohrbach Lake is itself an unnatural, man-made waterway, dammed in the 1940s and fed by higher-up springs to create its 17-acre expanse. Like much of Richmond Creek, it is now an unique oasis of nature in the urban landscape.

Nathan Kensinger is a photographer, filmmaker, and curator who has been documenting New York City's abandoned edges, endangered neighborhoods, and post-industrial waterfront for more than a decade. His Camera Obscura photo essays have appeared on Curbed since 2012. His photographs have been exhibited by the Museum of the City of New York, the Queens Museum, the Brooklyn Museum, the NYC Parks Department, and inside the Atlantic Ave-Barclays Center subway station.