Karasuyama Castle, Mountain fortress in Nasukarasuyama, Japan

Karasuyama Castle is a yamajiro built on Mount Hakkō at 202 m elevation, with the honmaru and ninomaru on the summit and five enclosures known as Gojō-sankaku. In 1659 Hori Chikayoshi added the san-no-maru at the eastern foot, with a palace and watari-yagura. Stone walls and earthen ramparts remain; the photograph shows a retaining wall of large irregular grey and brown boulders behind tall tree trunks.

Nasu Sukeshige built the castle in 1418; from 1514 it served as the residence of the lower Nasu branch until that line died out, then passed to the main Nasu clan. It withstood repeated Satake attacks, including the 1563 Omi battle and the 1567 Okurayama battle. In 1590 Toyotomi Hideyoshi stripped the Nasu of their holdings, and Oda Nobukatsu held the castle for two months. Abandoned in 1869, it lost its San-no-Maru palace to snow in 1872 and its remaining buildings to fire in 1873.

The nickname Gagyu-jo, "Lying Ox Castle", comes from the ridge's outline, said to resemble a reclining ox. The site also appears in Kawaguchi Matsutaro's 1946 novel "Hebihime-sama", whose title character is modelled on Oshika-no-kata, fourth daughter of Okubo Tadatane. The castle's Shinkami gate, a rear entrance, was moved and still stands.

The fortress grounds are accessible via a roughly 15-minute walk from Karasuyama Station, with stone walls and earthen ramparts visible throughout the public park. The terrain is hilly and uneven in places, so sturdy footwear helps navigating the site comfortably.

Karasuyama Castle was also called Gagyu-jo, "Lying Ox Castle", after a landform resembling a reclining ox. The castle withstood repeated attacks by the Satake clan and was never taken in battle. In 1590 Toyotomi Hideyoshi gave it temporarily to Oda Nobukatsu, a surviving son of Oda Nobunaga, who held it for about two months.