Starting in the South West of France then next to the Pyrenees you have the Pyrenees-Orientales department in the Languedoc Roussillon which borders Spain and is known for its Catalan culture. The best known seaside towns/villages are Cerbere, Banyuls-sur-Mer, Port Vendres, Collioure, Argeles-sur-Mer, Elne, Saint Cyprien, Canet en Roussillon and Le Bacares. Slightly inland you have the city of Perpignan with its 13th century Palace of the Kings of Majorca and its international airport.
Locations of particular interest here are the long beach at Argeles sur Mer and the Medievel castle in Collioure. Inland you have the Catalan Pyrenees National park, the hilltop Abbey of Saint Martin of Canigou and the Canigou Peak itself. Having the beaches and mountains in such close proximity to each other makes this a particularly beautiful and sought after area of the South of France and allows you to ski in the morning and be on the beach in the afternoon.