Trematon Castle, which was mentioned in the Domesday Book, has gone on the market with a 20 year lease. The site, owned by the Duchy of Cornwall, includes a Grade II listed house.
The grounds in Saltash include the remains of a Norman castle.
The gardens surrounding the home and the castle have received "extensive remodelling to give a magical feel", agents Knight Frank said.
The grounds feature wooden cannons, an outdoor pool and a two-bedroom lodge to rent out.
The property is on the market for £850,,000 which will secure new residents a 20-year lease.
Visitors to the property over the years have included the Queen and Sir Francis Drake, who stored treasure in the gatehouse.
