When the Golden Gate Bridge opened in 1937, the road leading to it, a hulking viaduct of concrete and steel known as Doyle Drive, split the northern tip of San Francisco in two, cutting right through the Presidio, the U.S. Army base that guarded the mouth of San Francisco Bay. For as long as the Presidio remained a base, the land’s division into two pieces wasn’t a huge problem.

But in 1994, the Presidio was decommissioned. The land has since been turned into a national park, and the buildings on it have been redeveloped as housing, restaurants, offices, art spaces, and more. With the Presidio thus transformed into a very public place, the fact that it was cut off from the nearby shoreline suddenly mattered much more. As it happened, Doyle Drive was in need of replacement, owing to a number of design flaws and damage from the 1989 Loma Prieta earthquake. This provided an opening to rethink the road’s role in the landscape. Various road-centric plans were initially considered, but it was an idea from a Bay Area landscape architect named Michael Painter, who proposed surrounding the road with a tunnel and then covering the tunnel with parkland, that garnered the most support.

“It’s created an incredible opportunity for us to stitch the two halves of the park back together,” says Michael Boland, the acting executive director of the Presidio Trust, which manages the park. The Doyle Drive replacement, completed in 2015, is tucked inside concrete tunnels, the roofs of which will serve as green bridges linking the two sections of the Presidio that were separated in the 1930s. (An existing surface street, Old Mason Street, still runs parallel to the shoreline, but is easily traversable by pedestrians and bicyclists.) The top of the now-covered road and the surrounding area will be landscaped by James Corner Field Operations, the landscape-architecture and urban-design firm behind New York City’s High Line. In the end, the Presidio will gain 14 acres of newly developed park space.