The Mozu Kofun Group is a cluster of ancient burial mounds in Sakai City, Osaka Prefecture. In July 2019, 23 kofun belonging to the Mozu Kofun Group were officially inscribed as a World Heritage Site. Built from the late 4th century to the late 5th century, the group forms the tombs of rulers of the ancient Japanese archipelago and includes many keyhole-shaped tumuli (zenpo-koen-fun) that are extremely rare worldwide. In addition to keyhole-shaped mounds, the site includes four types of kofun—scallop-shell-shaped, round, and square mounds as well—serving as a model for kofun found throughout Japan. While there were once more than 100 mounds, 44 remain today: 13 keyhole-shaped, 9 scallop-shell-shaped, 17 round, and 5 square. Among them, the Nintoku-tenno-ryo (also known as Daisenryo Kofun) is the largest in the world by area; it is about 486 meters long and takes roughly one hour to walk around. The Museum of Fine Arts, Boston in the United States houses items said to have been excavated from the Nintoku tomb, including a fine-line patterned mirror with animal-band motifs and a sword with a single-phoenix ring pommel. The name “Mozu” is said to originate from an anecdote in the Nihon Shoki: while the Nintoku tomb was being built, a deer leapt into the construction site and died, after which a shrike (mozu) tore at the deer’s ear and flew out.