The vessel that carried the first humans to the deepest part of the ocean in the Mariana Trench back in 1960 was named Trieste to honor the Adriatic port city where it was built.

After a recent visit, I decided the name couldn’t be more apt.

Everywhere you look in Trieste, there are signs of a people at one with the sea–from the thicket of masts rising up from the docks to the plates of tiny baked fish, ceviche-style octopus, and local mussels that adorn the tables at each outdoor café you pass. A grand canal welcomes small boats into the central square, further blurring the lines between land and water.

With its blend of Italian, Austro-Hungarian, and Slovenian influences, Trieste is a treasure borne from water–a real-life Atlantis that has something to offer the artist, historian, and nature-lover alike.

Here are some of the highlights of this delightful cultural crossroads:

View Images The Cathedral of San Giusto preserves pieces of Trieste’s long and storied past. (Photograph by Sarah Polger)

Trieste’s compact layering of architectural styles serves as a constant reminder of the city’s long history. At the waterfront, 19th-century warehouses are being refurbished and the harbor area reborn as one of Europe’s greenest ports.

On what is now a back street, crumbling ruins of a Roman amphitheater add a chaotic profile to the scene, providing cover for stray cats and ample ground for the area’s ubiquitous black-and-gray hooded crows to consort.

At the top of it all, on the city’s central hill, stands a building that serves essentially the same function as earlier structures that have occupied the site. Once home to a monument to Jupiter, Juno, and Minerva, members of the Roman pantheon, the San Giusto Cathedral, an active Catholic church, now stands in its stead.

The current structure, a melding of two basilicas built in earlier eras, retains facets from each stage of its past–from mosaic tiles dating back to pagan times to relief portraits from an ancient Roman family cemetery. A niche houses a third-century femur of San Giusto (Justus), the patron saint of the city, while medieval frescoes tell the story of Giusto’s martyrdom in pictorial form. Drop a euro in the box to turn on spotlights that bring out the artwork’s lavish colors and intricate detail.

View Images Miramare Castle on the Gulf of Trieste (Photograph by Sarah Polger)

When you’re cruising by in a boat, the crenellated outline of Miramare Castle stands out clearly against a dark scribbles of trees. Located five miles northwest of the center of town, this gargantuan 19th-century coastal mansion has been home to Austrian royalty as well as American soldiers in the aftermath of World War II.

Today it plays host to a stream of tourists seeking a glimpse of old aristocratic grandeur, devoted docents and groundskeepers, and, visible in the crystal-clear waters below, colorful fish that find in the surrounding marine reserve a home as beautiful as that above the waves.

Take a half-hour bus ride from the city center to visit a natural marvel far bigger than any castle or cathedral in Trieste. The Grotta Gigante is an appropriate moniker for the colossal cave. How big is it? Big enough for Italian David Cusanelli to BASE jump inside of it in 2013, parachute and all.

Five hundred damp, sometimes muddy, steps lead down to one of the largest (if not the largest) tourist caves in the world. When the view finally opens up, it’s difficult to make sense of the scale of the chambers until you realize that what looks like a frozen lightning bolt in the distance is actually the zig-zagging staircase back out.

View Images Race day at the Barcolana regatta in 2013 (Photograph by Sarah Polger)

The stalagmites rising from the floor are also unlike any you’re likely to have seen. As drops of mineral-rich water fall from the ceiling, they build up so much speed that they splash widely on the rock floor below, gradually building up layers that look less like soft-serve ice-cream and more like a stack of dishes.

For those looking for a bit more of an adrenaline rush than a walk through the cave, but not as much as BASE jumping in it, the surrounding mountains and cliffs offer many alternatives. To the west and north are several opportunities for rock climbing and mountain biking. And if you want something both outdoorsy and civilized, there are organic farms and Prosecco wineries to visit.

View Images Mauro Pelaschier at the helm (Photograph by Sarah Polger)

If you’re traveling in the fall, consider planning your trip to coincide with the Barcolana regatta. Held each year on the second Sunday in October, the celebrated event attracts spectators from all over who come to witness one of the largest sailing competitions in the world.

Mauro Pelaschier–a beloved local hero and the first Italian to compete for the America’s Cup–sees the race as the joyful culmination of a long competitive season as well as a fitting tribute to a sporting culture that has united the community despite changing borders and customs.

In fact, as war and politics divided the region and the younger generations began moving away from the traditional crafts and skills of their forbears, Mauro says the Barcolana was created to do just that.

Andrew Howley is a member of National Geographic’s Mission Programs team, working to share the stories of Nat Geo Explorers and grantees online. Follow his adventures on Twitter @anderhowl.