Urban Explorer (2011) on Netflix

Plot summary

Four young urban explorers from different parts of the world meet through the internet and gather in Berlin to see the underground relics of Nazi Germany. Their illegal tour follows a maze of tunnels, sewers and catacombs to a bunker called the Fahrerbunker, Hitler's subterranean garage and the center of many legends, where they hope to find forbidden Nazi wall murals. A local guide, Kris, leads the way. When he falls from a wooden bridge and breaks his leg, Marie and Juna go for help while Denis and Lucia, a nurse, stay with him. A stranger named Armin appears and offers to lead them out.