Vigo's location between the Portuguese border and the Galician interior makes it an excellent base for day trips in all directions.
Islas Cíes are the natural first choice — reachable by ferry from Vigo's port in around 45 minutes, and arguably the finest beach destination in Spain. Baiona (Bayona), 20 km south, is a walled medieval town where Columbus's Pinta first returned to Europe in 1493 — the replica ship is moored in the harbour. Pontevedra, 30 km north, has a beautifully preserved old town and is one of the best-kept secrets in Spain. Across the Minho River, the Portuguese city of Valença is reachable in under an hour and worth the trip for its intact star-shaped fortress and cheap shopping.
Further afield, Santiago de Compostela (95 km north) can easily be done as a day trip, though it deserves longer. The Rías Baixas wine country surrounding Vigo produces the finest Albariño in Galicia.