Dungcas Beach Defense Guns is located in Guam

The Dungcas Beach Defense Guns are an old World War II Japanese fortification in the United States territory of Guam. It consists of a tunnel dug in the coral limestone of the cliffs overlooking the beach on the northeast east side of Hagåtña Bay on the west side of the island. The tunnel has two guns mounted at openings facing the beach. This fortification was built by the 48th Independent Mixed Brigade of the 29th Division of the Imperial Japanese Army, during its occupation of the island 1941-44. The guns from this position were probably fired on landing Allied forces during the 1944 Battle of Guam, in which the United States retook the island.

• http://en.wikipedia.org/wiki/Dungcas Beach Defense Guns