The Greenwich foot tunnel links Greenwich with the former dockyards area on the Isle of Dogs.
The tunnel, completed in 1902, was designed to allow workers living south of the river in Greenwich to travel to work in the dockyards.
Bomb damage to the northern end of the tunnel during World War II led to repairs that restrict the size of the tunnel for a short distance.
It is an interesting way to return to central London from Greenwich by crossing the river and using the overground Docklands Light Railway to take in panoramic views of the now redeveloped Dockalnds and Canary Wharf areas. The entrance may be found close to the Cutty Sark.
Its has a twin at Woolwich which is similar but a little more scary, mainly due to the lack of peole using it!