Built in the 16th century to protect Old Grimsby Harbour, the Old Blockhouse saw action in the late stages of the Civil War, when Parliamentarians attacked the Royalist garrison. Today its substantial remains overlook a white sandy beach.
Read more about the history of the Old Blockhouse.
Before You Go
Access: The blockhouse is only accessible on foot, via a 20 minute walk from Old Grimsby along pleasant lanes.
Dogs: Dogs on leads are welcome.
Please be aware: English Heritage does not permit drone flying from or over sites in our care, except by contractors or partners undertaking flights for a specific purpose, who satisfy stringent CAA criteria, have the correct insurances and permissions, and are operating under controlled conditions.
There are steep and uneven steps up to the Blockhouse entrance, with sheer drops from inside the ruins.
Plan a Great Day Out
Refreshments are available from a well-stocked shop just south of New Grimsby harbour - why not put a picnic together and enjoy it on the vast white sandy beach.
Take time to discover the island's two castles on the western side of the island. Cromwell's Castle and King Charles' Castle are situated just north of New Grimsby Harbour. Along with the Old Blockhouse, these two sites can be included on the six mile circular coastal walk around Tresco.
Call in at the Isles of Scilly Museum in Hugh Town, St Mary's, for more information about the history of the Isles.