The hill at O Castro is where the first inhabitants of Vigo settled and could be considered the place where the city was started. The archaeological remains of 45 stone castro dwellings from the second and third century B. C. can still be seen on the right slope of the hill.

During the Middle Ages, a castle was built at O Castro. It was built at the same time as the Castle of San Sebastián and the fortress that joined the two. The fortress of O Castro was made up of three walled enclosures. Now only the first and part of the second remain. The third, which was the wall of the city, has completely disappeared.

The first enclosure is the fort at the top of the park which is now a garden with some wonderful views of the bay. Here we can see the Monument to the Vigo Spirit and another dedicated to the local stone masons.

The second enclosure is the fort of San Sebastián, where the Town Hall now is at Plaza del Rey. A network of tunnels was found connecting the castles with each other and the city.

In O Castro there are monuments to Curros Enríquez, the great 19^th century Galician writer, Martín Códax (a medieval troubadour); the Galleons of Rande, a monument commemorating the Battle of Rande in 1702; a cross to the "Caídos" (a monument in honour of the victims of the Spanish Civil War), and others.

The park is also a wonderful botanic garden and has a great variety of autochthonous and foreign plant species. The most important of these are pine, cedars and camellias.