As reported by Space News, the China Astronaut Research and Training Center (CARTC) just wrapped up a month-long training regimen meant to prepare future and veteran astronauts for lunar landing missions. While it isn’t known which cave the astronauts braved, the CNSA notes the system was located somewhere in the Wulong District of Chongqing. One of the directors of the Chinese cave training, veteran astronaut Ye Guangfu, also participated in a 2016 CAVES training in a European cavern. “Compared with the cave training in Europe, our support team inside the cave intervened as little as possible,” Ye told the state news agency Xinhua. “In that kind of darkness, the mental pressure is overwhelming.”More on China: China Installs Defensive Countermeasures on Space Station