Route your belts freely underground.
Mods introducing new content into the game.
Augmented or new ways of transporting materials - belts, inserters, pipes!
Crashes on use https://imgur.com/PXHJsjE errors
Thanks for the report. This appears to happen when Nanobots builds the ghost of an underground belt (on the surface), but the location in the underground is already occupied. I believe I have it fixed now.