Malessu' Pillbox - Credit: Wikimedia Commons
The Malessu' Pillbox is a World War II-era Japanese-built defensive fortification on the shore of Malesso', Guam. Located about from the high-tide line at Merizo Beach, it is a rectangular structure built of steel-reinforced concrete and basalt rock. It is deep, wide, and about high, although only about of the structure is visible above ground. Its gun port has a view of the Merizo pier, and is approximately at ground level. It was built by Japanese defenders during their occupation of the island 1941–44. Read more on Wikipedia
Source: en.wikipedia.org