Onomichi Castle is not a historic site but was built in 1964 by the president of Onomichi Chamber of Commerce and Industry as an observatory and history museum. Influenced by the restoration work of the donjon of Fukuyama Castle in the adjacent city, this castle was constructed at this place by modeling after Fukuyama Castle. This Irimoya-styled steel reinforced concrete donjon with three stories and three floors is located on the hill to the north of Onomichi station. As it is outstanding from a distance, it once became a symbol of the city. However, the castle was closed in the 1990s due to the management failure and has fallen into ruin. Though not having historical value, the building itself is fine, so a new use is expected to be found by the municipal government in the near future.