St Just-in-Roseland is situated in the Deanery and Hundred of Powder. It is bounded on the North by Philleigh, on the East by Gerrans and Gerrans Lake, on the South by St Mawes Creek and St Anthony's Pool which separates it from St Anthony, and on the West by Falmouth harbour and the ocean. The parish is set on the Western side of the Roseland. To the West is the Carrick Roads a large natural harbour with the port of Falmouth on its Western side. The town of St Mawes, which is the chief place of residence, lies within the parish; it stretches along the shore line on the North side of Falmouth harbour. The parish contains a castle, called St Mawes Castle, which was built by Henry VII1 in 1542. It is one of a pair, commanding Carrick Roads seaway and the entrance to Falmouth harbour, the other being Pendennis Castle at Falmouth. St Mawes has its own harbour where ferry services connect it with Falmouth and St Anthony and Gerrans.