By The Cornwall Guide. Last updated 12 Jan 2022 16th-century fort built over St Mary's Pool harbour, but never finished Facebook Twitter Pinterest WhatsApp Select ratingGive Harrys Walls 1/5Give Harrys Walls 2/5Give Harrys Walls 3/5Give Harrys Walls 4/5Give Harrys Walls 5/5 No votes yet Location Isles of Scilly Isles of Scilly Go to website » Attractions near Harrys Walls King Charles Castle Cromwell's Castle Garrison Walls The Old Blockhouse Tresco Abbey Gardens