I read a comic or graphic novel about a year ago in a bookshop, and vaguely remember the following events in it:
- Construction workers extending a sewer system or something underground experience some problems and call their boss.
- They explain to the boss that while digging they came across a wall that's built like a vault with a steel frame and x feet thick concrete etc.
- The boss tells them to keep going (I think).
- It is the Batcave on the other side... or if I'm truly mistaken, Superman's Fortress of Solitude.
I don't remember the year of publication though.
Which comic is this?