The tunnels which run beneath the city centre. The tunnels were built in the 1842. Learn about the history of the tunnel. Tour takes a couple of hours. Be prepared for a cool dark enclosed space with a low space with uneven floors. You meet at an office and walk down the canal side while the guide talks about wartime local history. One volunteer tour guide talked mostly about wartime, then the other talked about the tunnel's original purpose. Both guides knew their subjects well. You then get a hard hat and torch to use in the tunnel. Enjoy the use of sound / theatrics to help supplement stories by the guides. Fascinating history that you'd never imagine. You have to book in advance. Hard hats and torches are provided.