The Broomway is a historical byway open to all traffic across Maplin Sands in Essex, linking Great Wakering (near Shoeburyness) to Foulness Island. It is only passable at low tide, and is dangerous to use in conditions of poor visibility, with OS maps advising to seek local guidance.
The route was the only access to Foulness Island until Havengore Bridge, and takes its name from the 400 or so brooms that were placed at intervals of between 30-60 yards on either side of the track to indicate the route of safe passage.
The Broomway is surrounded on both sides by quicksand and deep, sucking mud. It has no markers and no guideposts. And if you mistime your walk, you won't outrun the tide. Oh, and it's in the middle of a Ministry of Defence firing range. But most of the time, if you want to visit Foulness Island, it's the only way.