The Sunken Bridge That Lets You Walk Through a 17th-Century Moat

From a distance, there’s nothing to see. Just a grassy fortress mound, a still moat, and open water stretching between the two. Walk closer, though, and a narrow trench opens up in front of you, cutting straight through the water at ground level. Step down into it, and you can walk clear across the moat without so much as getting your shoes wet — the water rising in walls on either side of you, level with your shoulders.

This is the Moses Bridge, one of the more quietly ingenious pieces of design to come out of the Netherlands in the last two decades.

A Fort That Wasn’t Supposed to Have a Bridge

The bridge crosses the moat of Fort de Roovere, part of the West Brabant Water Line — a defensive network of fortresses, moats, and floodable land built in the late 17th century to protect towns in the southwest Netherlands from French and Spanish forces. The system’s logic was simple but effective: engineers flooded the land around each fort to a carefully calculated depth. Too deep for soldiers to wade or march across, but too shallow for enemy boats to sail through. An attacking army had nowhere to go.

Like much of the water line, Fort de Roovere fell into disrepair over the following centuries and was eventually restored as a public recreational site, connected to regional cycling and walking routes. That restoration created an obvious problem: the fort needed a way for visitors to cross the moat. But a conventional bridge — an arched structure rising above the water — would have defeated the entire point of the fortification. As the architects who took on the project put it, building a raised bridge on the side where an enemy was expected to appear would have been “highly improper.”

Designing an Invisible Bridge

The commission went to Dutch firm RO&AD Architecten, led by architects Ro Koster and Ad Kil, working with the municipality of Bergen op Zoom. Their solution, completed in 2011, was to skip the idea of a bridge rising over the water entirely and instead sink the walkway below the waterline.

The result is a wooden trench — built from Accoya, a modified, highly durable wood, and waterproofed with EPDM rubber sheeting — set into the moat so that its walking surface sits lower than the surrounding water. Retaining walls on either side hold the water back, letting pedestrians walk through a dry channel while water flows on either side of them at eye or shoulder level. Because the structure never breaks the skyline of the fort, it’s essentially invisible from a distance; the water and the earthen slopes of the fortress appear to run together uninterrupted.

The effect on arrival is part of the design’s appeal: visitors don’t see a bridge, they see a fortress rising out of open water — until they’re close enough to notice the trench cutting through it. The name Moses Bridge captures the reference directly: walking through it feels like walking through parted water.

A Small Structure With Outsized Recognition

At just 50 square meters, the Moses Bridge is modest in scale, and its total construction cost was reported at around €250,000. Despite its size, it earned the Build of the Year award from the BNA, the Royal Institute of Dutch Architects, in 2011, and has since become one of the most-photographed pieces of contemporary architecture in the country — an unusual case of a defensive structure’s original logic (staying hidden) becoming, centuries later, exactly what makes it a tourist attraction.

Today, Fort de Roovere and its bridge are open to the public near Halsteren, in the municipality of Bergen op Zoom, as part of a network of walking and cycling trails through the restored water line.