Reached via glass-topped domes (with lifts and steps) on either side of the River Thames, this white-tiled 370m-long pedestrian tunnel opened in 1902 provides an atmospheric route to Greenwich from the Isle of Dogs; it's also an excellent diversion to get a photo of Greenwich from the north side of the river. At an average walking pace, the journey is only around 10 minutes but can be done faster, especially if you aren't keen on the feeling of the river just 15m overhead.
Look out for the WWII bomb damage at the northern end of the tunnel, which was fixed up with a steel and concrete lining. About 4000 crossings are made by pedestrians every day. There is another foot tunnel under the River Thames at Woolwich to the east.
