In the hillfort, the houses are made of stone and are circular, with a central fireplace. They were built very close together. The palstave axes that are on exhibit in the Sala de Muelle in the Galicia Museum of the Sea correspond to the earliest occupation of the hillfort. These items were used as currency and traded between the peoples along the Atlantic coast of Europe. A bucket, which was excavated in the furthest part of the hillfort, is an example of the archaeological remains from the 4th Century BC. The three vertical stones - where pottery from southern Spain was found - may have been part of an Ibero-Punic altar. The hillfort was abandoned at the start of the 1st Century BC. At this time, Roman villas were starting to be built around this area. Fish was salted at these villas - one of the oldest links between the city, the surrounding area and maritime industries. The site is between the two buildings which made up the Galicia Museum of the Sea. There is a panoramic view from the O Castro hill, and you can see other sites such as Cíes, Darbo, Domaio, Vigo and A Guía - in fact, you can count as many as ten