本郷ふじやま公園, Park with historic farmhouse in Sakae Ward, Yokohama, Japan

Hongo Fujiyama Park is a district park in Kaji-ga-yatsu, Sakae Ward, Yokohama, covering a small wooded hill that rises above the lowland of the Itachi River. At its centre stands the former Koiwai family house, a thatched-roof farmhouse moved here from the old Kaji-ga-yatsu village, with a low stone wall and gravel forecourt in front. An archery hall also stands on the grounds.

The farmhouse was built in 1847, as confirmed by a dismantling survey, and was designated a Yokohama City Tangible Cultural Property in 2002. It was moved from the former Kajigaya village to the park's old farmhouse zone. The storehouse was rebuilt from a family layout plan, and the nagaya gate was restored to thatch after a trace survey.

The name Koiwai comes from the family that owned the thatched farmhouse, built in 1847 and moved here from the old Kajigaya village. Inside, three connected tatami rooms lead to a hall, a Buddhist altar room and a storeroom, with a low attic above them. The storehouse behind the main house was rebuilt from an old family layout drawing.

The park lies in Kaji-ga-yatsu, Sakae-ku, Yokohama, in the lowland facing the valley of the Itachi River. The old Koiwai house opens 9:00-17:00 and is generally closed Wednesdays and over the New Year holidays. The archery hall opens 9:00-18:00 and is generally closed the fourth Monday and over the New Year holidays.

The main house was dated to 1847 by dismantling surveys, and its three-room zashiki, wide hall, Buddhist altar room and storeroom sit under a tsushi-nikai attic. The rear kura had already been lost before the house was moved, so it was rebuilt from a family house-plan diagram.