They definitely have a lot of tunnels under the airport. I was a subcontractor that had to work in various locations around the airport. We had our own golf carts to drive through the tunnels to move construction stuff. Its super easy to get lost down there everything looks the same and its huge.

Edit: I had a id that let me go almost anywhere and never saw anything strange. There were quit a few spots that were off limits though (I'd wouldnt unlock door & no windows) the murals are weird and there is a lot. This could also get my id taken away but I won't be working there again anyway.

There is also a side gate were they take illegals and put them on and as well as con air. More than likely using it to move them around instead of sending them back.