I don't know how true it is, but there are rumoured to be lots of catacombs and tunnels under the city.

Certainly, where I live (outskirts of the city) there are a few. There's one between the local pub and the church (really!) and one between an industrial unit and a bank was used to commit a robbery before it was filled in.

When Morris Engines old site at Bell Green was built on, the developers were worried about hidden tunnels and unknown basements and requested information from any of the old workforce. I know that the old Triumph factory at Canley had extensive underground passages and cellars and it has long been rumoured that Alvis on Holyhead Rd had an underground hospital.

When I worked at Austin Rover, the underground works at Longbridge were quite something to see and Land Rover at Solihull had a massive shooting range under one building.

Very often these things are undocumented and as staff leave/retire the information goes with them.

There'd be a lot of interesting history surrounding them. Shame they couldn't have slotted into the city of culture fiasco; but then, the visitor centre showing the cathedral's archaeology was shut down because the city council decided to stop funding it, so I'm not surprised.

I've been into a couple of them. Imagining hiding down there as ordnance fell was rather disconcerting.

Interesting looking structures - worth looking around when they reopen: https://www.coventrytelegraph.net/news/coventry-news/coventry-cathedrals-forgotten-crypts-19627731