Williamson's Tunnels, Paddington

Joseph Williamson spent the early 1800s paying men to dig tunnels under Edge Hill for reasons nobody has ever fully explained, and over the following century the tunnels were sealed and forgotten. The Friends of Williamson's Tunnels rediscovered the Paddington chambers in 1999, and their volunteers spent four years emptying tonnes of infill out of them. The tour goes down through four storeys of sandstone to a chamber 12 metres high and 18 metres below the street.

Tours run on Wednesdays and Sundays only, are free to individual visitors and are booked by email or the online form rather than by phone. Allow two hours for a 90 minute tour with plenty of steps and some uneven floors. That makes it a trip for school-age children with a bit of patience rather than toddlers, but the ones who like a mystery tend to come out with a lot of questions.

The Williamson Tunnels Heritage Centre on Smithdown Lane is a different organisation running its own paid tours Friday to Sunday, which is why the brown signs cause so much confusion.

What it costs: Paddington tours are free for individuals, with donations welcome. Groups of six or more pay £5 a head in advance. Extended tours of the house site and Banqueting Hall are for members, and you can join on the day.

Worth knowing: Lots of steps; sensible shoes required.

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