Weird experience, not for claustrophobic tourists. The tunnel seems to be frozen in time (the escalators have wooden steps), everything kept as it was originally built, in the art deco style of the 1920's.
Fantastic building on the old city side of the river with a wooden lift and interesting architecture. Would not matter if you walked through but we cycled in a circular route through a couple of different tunnels as St Anna's is not the only one but the most interesting.