This stubby four-storey tower was originally part of a defensive complex built by the local Salazar family during a period of baronial fighting in the 15th century. It subsequently served as the family's fortified residence, and was rebuilt following a devastating fire in 1934. Today it houses a small museum with a few display case on Portugalete and the Salazar family. Most interesting is the model of the village (then walled) as it looked in the 17th century.
Don't miss the fine views from the fourth floor. There's also a top-notch restaurant on the ground floor.