Castle Rosanbo in Lanvellec. Just a few steps away from Lieue de Grève lies Rosanbo, still one of the most important castles in Brittany today. This large quadrilateral building was constructed over 6 centuries and is surrounded by magnificent French gardens bearing the label “Jardin remarquable” (extraordinary gardens). Its vaulted hedges stretch over 2.5 km (1.5 mi.) and are among the longest in France! The castle is open from April to October. You may visit it on your own or with a guided tour.