Built in 1921 underneath what was the Tram depot but now Halifax Bus Garage it included a brick vaulted basement running under three of the depot bays and the external yard. The basement was roughly triangular in shape consisting of five parallel vaulted tunnels, each one slightly longer than its neighbour. The three longer tunnels (under the depot) had a stairway into the tram bays above. The two shorter tunnels under the yard were accessed by a single stairway at one side. There is a cross corridor linking the tunnels.
Another website link (above) explains the situation with:-