Once upon a time, this 252-foot-long tunnel provided an escape route for intrepid travelers on the south side of Canal Road looking to access the north side near the Foundry Branch Trolley Trestle, which once carried commuters from Georgetown through Dalecarlia and on to Glen Echo, once home to a popular amusement park. Nowadays, the tunnel is a murky, poorly-lit passage that connects the Capital Crescent Trail and C&O Towpath to the northern side of Canal Road. It’s still a very useful thruway for pedestrians and cyclists who need a…