Arai Castle

Arai Castle is a Japanese castle ruin sitting on a 26-meter (85-foot) high promontory on the western coast of Miura Peninsula. The fortification stands between Koajiro Bay and Aburatsubo Bay, positioned to command the surrounding waters and passages.

The castle fell in 1516 after a three-year siege by Hojo Soun forces, ending Miura clan control of the area. This shift in power marked a turning point in the region's feudal politics and territorial control.

The name Aburatsubo comes from the dark water that appeared during the final battle, resembling oil in a container. Walking around the bay today, you can still see how the local geography shaped this powerful memory.

Visitors can reach the castle ruins by taking a Keikyu bus from Misakiguchi Station to the Aburatsubo terminal, then walking about five minutes on foot. The site requires basic hiking shoes because pathways on the hillside can become steep and uneven, especially after rain.

The grounds now house the University of Tokyo Marine Research Laboratory, blending historical fortifications with modern scientific study. Along the hiking trails, you can spot remnants of moats and earthen ramparts that reveal the site's military past.