The Greenwich tunnel is a subterranean footpath that undercuts the River Thames and has remained unknown to many. Starting from the North Tower, this tunnel runs from the Isle of Dogs all the way to Cutty Sark Gardens in Greenwich. Back in the 1900s, the tunnel was built to serve as a replacement for the costly and unreliable ferry service. This provided workers living south of the river an alternative route to reach their workplaces in the docks and shipyards around the Isle of Dogs. Due to significant bomb damage sustained during World War II, the diameter of the tunnel is noticeably reduced on the northern side. During the repairs, parts showing exposed metal ring segment linings had to be installed. A quick way to get across from one side of London to the other.