Tahara Castle was founded in the late 15th century; today the surviving grounds are modest, with reconstructed gates, stonework, and a local museum. It is not a castle to cross Japan for, but it gives the town centre a historical anchor before or after the coastal drive.
The museum is strongest if you want context on the area's local history and art. For most visitors, the castle works as a short stop paired with lunch in town or the ride out to Mount Zao.