Visitors are now able to stroll through the now-defunct Leicester-Swannington Railway tunnel and discover the history behind the historic structure.
The Glenfield Tunnel, built in the early 1800s, runs for a mile beneath Leicester's streets and has been closed since 1966.
David Lyne, from the Leicester Industrial Historical Society gave the group a guided tour of the tunnel, explaining its history and the project which has brought it back to life.
Leicester City Council bought it for just £5, and spent £500,000 restoring its crumbling walls to meet safety standards.
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It will be a fine evening with clear skies, although turning cooler as the sun goes down.
Remaining dry with clear spells overnight and sunny spells on Tuesday.