The ruins of a castle built by Toyotomi Hideyoshi in 1590 during his campaign against the Hojo clan of Odawara — famously constructed in secret and revealed overnight to demoralise the besieged city. Only stone walls and foundations remain, but the hillside setting, with views across Sagami Bay and the Izu Peninsula, is striking. Historians of Japanese unification will find this a moving site; the ruin marks one of the decisive moments of the Sengoku period.
About 30 minutes by foot or taxi from Odawara. Free admission.