St. Mawes Castle has magnificent architecture and a breathtaking waterside setting. It is the most picturesque and complete of King Henry VIII's coastal fortifications. St. Mawes Castle was built four hundred and fifty years ago between 1540 and 1545 about the same time as its twin, Pendennis Castle, which stands across the estuary. St. Mawes consists of a central tower with lower bastions attached on three sides in a sort of three-leafed clover pattern. It is decorated with carved inscriptions, coats of arms, and has gargoyles protecting the entrances.

Architecturally the most decorative of all Henry VIII's castles St. Mawes was still built for defense and the gun decks are well designed. The remains of a small blockhouse are at the water's edge together with batteries of the 1780's. A battery for four, twelve- pounder quick-firers of 1905 lie to the rear.

The grounds of St. Mawes Castle are now a beautiful garden where the visitor is tempted to sit and linger for a while. The views of the castle and of the bay beyond are lovely.