The east side of the outer castle along the Naka River was fortified by stone walls which were about 10 metres (33 ft) high and more than 700 metres (2297 ft) long. At the midpoint of the stone walls, at the entrance from the Nakajima-nishi Bridge, was the Higashi-toriire Gate. The Higashi-toriire Gate was composed of the Kita-mon (the North Gatehouse), the Minami-mon (the South Gatehouse), and a "yagura". (A gateway structure where a "masugata" gateway has two gatehouses facing each other, or where a "yagura" is placed facing the front of a "masugata" gate forecourt, is unique.) This grand gateway and the stone walls of the newly built capital of Chikuzen looked down on and strongly dominated the city of Hakata, which had a very long history as a mercantile city. An old book indicates that there was a Roman Catholic church near the gate, within the walls. This may be the church built in memory of Kuroda Josui, which is mentioned in an annual report of a Jesuit missionary to Japan.