I've been working on these for a while. I hope to have it included in the next update. Still, a lot of testing going on since it has to load even on very old phones.

Here is a screenshot of the tunnels from the top that should serve as a map. It will also have its own mission once it is fully tested. It has two entry/exit points and it is pretty large by walking distance.

 

And here is a screenshot in the editor of one of the entrances