The Illas Ons sit at the mouth of the Ría de Pontevedra, a low scatter of rocky islands inside the Atlantic Islands of Galicia National Park. Day visitors arrive by ferry from Sanxenxo, Portonovo, or Bueu through the summer months. The main island has a handful of pristine white-sand beaches, low cliffs on the Atlantic side, and a small village with two or three restaurants serving the day-trippers.
The walking is the reason to come. A network of marked paths circles the island — three or four hours will take you round the cliff tops, past the lighthouse, and back through the heather. Visitor numbers are capped and the official tickets must be booked in advance through the national park website during high season; the ferry company handles this for you when you buy a return.