Simplify the following text for a Grade 7 native English-speaking person.
Original: Saint-Martin-de-Castillon is a commune in the Vaucluse department in the Provence-Alpes-C Ã te d'Azur region in southeastern France .
Simplified: Saint-Martin-de-Castillon is a commune . It is found in the region Provence-Alpes-C Ã te d'Azur in the Vaucluse department in the south of France .