A tomb moat is a pond with a purpose, and over the centuries it has become something else: a habitat. Genemonyama Kofun is another of the Sakai mounds, and what strikes you first is the water, dark green and quiet, with lotus pads in summer, ducks in winter and grey herons standing at the edge. The moats were dug to separate the tomb from the world and to supply earth for the mound, and farmers later used the water for irrigation, so that the tombs became part of the local water system. Today they shelter fish, turtles, kingfishers and a surprising amount of insect life.
The mound itself is a wooded hill that few people climb, because entry is restricted, but a path runs around the outside, and there are places where you can glimpse the slope and the old stone steps. Autumn brings red and gold leaves, winter brings migrating ducks, and spring brings a haze of blossom. The sound of the neighbourhood, with trains, school bells and the clatter of bicycles, mixes with birdsong.
Riding here is straightforward and slow. Sakai is flat, and the roads around the tombs form a grid with a few busier arterial roads, where traffic from the port moves in heavy lines. The surfaces are good and signage is clear, though the roads are often narrow. Parking for bikes is limited and sometimes expensive, so use paid lots. In June the rainy season brings long grey days, and in late summer typhoons can flood low roads, so check the forecast.
With nearly eight hundred thousand inhabitants, Sakai has services everywhere, and a bowl of noodles or a plate of takoyaki, the octopus balls of Osaka, is never far away. For something quieter, ride out to the hills on the south-east edge of the city, with their reservoirs, cedar woods and small farms. Early morning is the best time to see the moat, when the mist lifts and the herons are still, and weekdays are quietest.