Also known as: Ishigaki-yama One-Night Castle (石垣山一夜城), Taikou One-Night Castle (太閤一夜城)

The One-Night Castle was Toyotomi Hideyoshi's stronghold during the Siege of Odawara, built on top of Mt. Ishigaki. 30,000 - 40,000 of Hideyoshi's troops began construction on it on April 5th and completed it in about 80 days. The construction was completed in secrecy, and its position within the tree cover of Mt. Ishigaki could not be seen from Odawara Castle to the north-east. At its completion, Hideyoshi ordered the trees felled so that from the Houjou side the castle seemed to spring up overnight, sapping their morale. The castle, the first all-stone castle in the Kantou, was very much a modern fortress at the time. Hideyoshi held tea parties at the castle with the imperial messenger as a guest.

The castle remains were designated a historical landmark in 1959.