Complex sentence: The oldest surviving corral in partial ruins is the Corral de Comedias de Alcalá, while the only functioning comedy theater still standing is the one in Almagro, which annually celebrates the "Festival Internacional de Teatro Clásico" (International Classical Theatre Festival).
Split into simpler sentences: The oldest surviving corral in partial ruins is the Corral de Comedias de Alcalá. The only functioning comedy theater still standing is the one in Almagro, which annually celebrates the "Festival Internacional de Teatro Clásico" (International Classical Theatre Festival).