Please help DARPA find a new underground research lair

Allodium The Defense Advanced Research Projects Agency (DARPA) puts out lots of public requests for scientific research, including high-profile competitions involving robotics and space launch tech. But today, the agency tweeted a very simple plea: it needs a massive, maze-like underground facility for running experiments, and it needs it right now.
What kind of facility, exactly? Well, “the ideal space would be a human-made underground environment spanning several city blocks [with] comp