Soldeu (or the isolated hotel at Grau Roig, up the road) is arguably the best places base to explore the extensive Grandvalira area. Soldeu is set on a steep hillside facing the ski area across the valley. It is on the busy road that runs down the valley from France to Andorra la Vella and on to Spain.
The Grandvalira ski area is shared with several alternative bases. Chief among them is Pas de la Casa, near the French border; El Tarter, a few miles down the valley from Soldeu, also has both lifts and return pistes. Further down still, Canillo and Encamp have gondolas but no pistes. Outings to other resorts in Andorra are possible - Arcalis in particular is worth the trip, but it's easiest by car. The Ski Andorra pass covers them all.