Cromwell's Castle - Tresco Cromwell's and King Charles Castle - Tresco Bryher to Tresco - Cromwell's Castle view 17th-century round tower positioned on a rocky promontory guarding the anchorage between Bryher and Tresco. 5 Rate Location Tresco Isles of Scilly Isles of Scilly Go to website » Attractions near Cromwell's Castle King Charles Castle Harrys Walls Garrison Walls The Old Blockhouse Tresco Abbey Gardens