The MARCO (Museo de Arte Contemporánea de Vigo) occupies a beautifully converted 19th-century prison building in the Casco Vello, a few minutes' walk from the waterfront. The permanent collection focuses on Galician and Spanish artists working from the 1960s onward, with particular strength in conceptual and video art. The temporary exhibition programme is ambitious for a city of Vigo's size and regularly brings in work from across Europe.
Entry is free, and the building itself is worth visiting for the architecture alone — the original vaulted corridors and the restored central courtyard make it one of the most interesting conversion projects in the region. Plan an hour for the permanent collection; longer if there is an exhibition you want to see properly. The museum shop stocks good art books and prints.