From The Link: Lessons Learned From the SubT Challenge

As the countdown started, a boxy robot with four big wheels carrying a host of cameras, sensors, communication equipment, autonomy software and the computing power to make it all work together rolled down a ramp into a dark tunnel. It did not know where it was, what was ahead of it or where it was going. It was there to explore. Over the next hour, more robots followed: wheeled robots, drones and a dog-like quadruped. Team Explorer deployed eight robots for the final round of the Defense Advanced Research Projects Agency (DARPA) Subterranean, or SubT, Challenge -- a three-year competition during which teams from around the world raced to develop robotic systems that could autonomously operate in underground environments like caves, mines or subway stations for search and rescue missions.