The National Park of Sant Maurici and Aigüestortes is must visit of the area.
The park can be accessed through Espot, that is, 15 minutes away by car. Depending on the season and the weather, you will be able to park in the upper parking or you will have to park near the Village. From the Village, there is a taxi that brings the people to Sant Maurici Lake. If you prefer walking, there is an alternative way from the village that avoids the main road to Sant Maurici Lake. (it will take you 2 hours to arrive). From Sant Maurici, you can continue the way to the waterfall of la ratera or you can head to the ratera lake and the lake lookout.
It is important to remark that, in winter, you will probably need snowshoes or mountain sky from certain point of the way. You can find more information here.