If you go to Mont Perdido National Park, then you shouldn’t miss the small town of Aínsa, which is voted by the public as one of the most beautiful towns in Spain (uno de los pueblos más bonitos de España).
The old town of Aínsa is built on a small hill and consists of a series of tightly packed houses, churches and towers. The huge and complete city wall surrounds the town, making people feel like they are back in the Middle Ages. The Mediano Reservoir not far from the town is also very beautiful. You can see the church bell tower that was mostly submerged due to the construction of the reservoir.