The Berlin tunnel 21 is a true story. This tunnel was used by the Nazis during World War II to transport troops and supplies between Berlin and the front lines. The tunnel was discovered by the Allies in 1945, and has since been turned into a museum. The Berlin tunnel 21 is a true story. This tunnel was used by the Nazis during World War II to transport troops and supplies between Berlin and the front lines. The tunnel was discovered by the Allies in 1945, and has since been turned into a museum. The Berlin tunnel 21 is located in the city of Berlin, Germany. The tunnel stretches for 21 kilometers (13 miles) beneath the city, and was used by Nazi soldiers to travel between the front lines and their base in Berlin. The tunnel was discovered by the Allies in 1945, and has since been turned into a museum. Visitors to the museum can see the original equipment used by the Nazis, as well as learn about the history of the tunnel and its importance during World War II.