We never got photos because it was 45 years ago but as teens we found a similar area below Chicago near six corners, many tunnels and ladders going lower and lower revealing more tunnels and more ladders going even deeper. We found "CD" Civil defence bunkers.

I bet they are still there.

>>8861730

In the alleys around six corners they have sewer caps that don't have drain holes like most do. We found many ways in by looking for the right type of sewer caps. if you pop a cap and see a ladder and no water your in. We were scared shitless the first few times we went down.