Sewer Tunnels/Subway Tunnels

[G0ads]

Since sewer entrance pieces were introduced in the city wasteland biomes, why not have sewers? Just break the entrances to the tunnels to get in. Subway tunnel entrances and the tunnels themselves could be really cool. You could have small camps set up in station areas similar to the ones found outside in forest and snow biomes as well as even overrun military checkpoints infested with the undead. In multiplayer, these features could be devastating to a team that has built a base inside a city as a rival team could use these systems to assault from different directions or even come up from underneath.