The herring fishing industry played a major role in the history of Otaru since the early days of the town's development, with the vast majority of fish being processed into fertilizer rather than consumed by humans. Large fortunes were made by the leading fishing enterprises until the 1950s, when the herring stocks dramatically declined and the industry collapsed.
During the heyday of herring fishing, large Herring Mansions (鰊御殿, Nishin Goten) were built by wealthy fishermen to process the fish and as a residence for themselves and their employees. A large preserved herring mansion dating back to the end of the 19th century stands on a hill beside the water about five kilometers outside central Otaru. It was moved to its current location in 1958 and is open to the public. Fishermen's tools and living conditions are displayed inside.
About a kilometer inland from the herring mansion stands the Former Aoyama Villa (旧青山別邸, Kyū Aoyama Bettei), a luxurious villa built by the Aoyama family, one of the most successful families in the herring fishing industry. The family spared no expense in the materials and construction of the villa and surrounding gardens. The Aoyama family's herring mansion was also preserved, but it was moved to nearby Sapporo where it can be viewed in the Historic Village open air museum.
The Herring Mansion and Aoyama Villa are located five kilometers outside of the city center near the Otaru Aquarium. They can be reached from Otaru Station by city bus number 10 or 11 (20-25 minutes, 220 yen, 2-3 buses per hour) or by Otaru Stroller's tourist buses (30 minutes, 220 yen, 1 bus per hour). From the Otaru Aquarium terminal stop it is a five minute walk to the Herring Mansion and a 15 minute walk to the Aoyama Villa. The Otaru Stroller's buses also stop in front of the Aoyama Villa.