Ruined Great Dwarven City Bridge

Publisher's blurb:

This huge city bridge, built within a giant underground cavern, is in ruins and pockmarked with holes. The remains of sprawling buildings still cover it. Three levels showcase the top story buildings with roofs, the abandoned interiors of the buildings, as well as the understory of the bridge with a sprawling undercity complex of decrepit boardwalks and abandoned taverns.

While your players travel the underdark they randomly encounter a group of dwarves seeking to demolish this bridge–and cut off the dark elves supply of slaves from their village. However, not everything has gone as planned, and they ask your players for help.