The largest keyhole-shaped burial mound (kofun) in Japan, the tomb believed to contain the remains of the fourth-century Emperor Nintoku is a whopping 840 metres long and 654 metres wide, making its entirety impossible to view from ground level. An outline of the massive mound, which is part of the Mozu-Furuichi Kofun Group World Heritage site, can be made out from a lookout platform in the surrounding Daisen Park, while a more comprehensive view can be had from the observation lobby on the 21st floor of the Sakai City Hall building.
Some 100 kofun in various shapes and sizes are thought to have been built in what is now the city of Sakai between the fourth and sixth centuries. Forty-four of these tombs remain intact today, and many can be visited. If you’re interested in kofun-hopping, it’s a good idea to ask for details at the City Hall building’s tourist information centre after your visit to the observatory.