Very early in the 13th century, inhabitants of what is now known as the Island of Tongatapu, Kingdom of Tonga, built this impressive 12-ton structure. It is the Ha’amonga Trilithon, a 5-meter-high limestone coral “gate” whose purpose is not known. (Some think it may have been the entrance to the king’s palace-and-garden complex.)
Twenty-five readers sent in correct answers, and STAN BACH of Washington, D.C., won the drawing. We thank Phyllis Tapscott of Indianapolis, Indiana, for sending in the photo.