Cromwell's Castle 
“The castle stands guarding the lovely anchorage between Bryher and Tresco and is one of the few surviving Cromwellian fortifications in Britain.…” – official site
Ease by public transport:
Unknown
“The castle stands guarding the lovely anchorage between Bryher and Tresco and is one of the few surviving Cromwellian fortifications in Britain.…” – official site
Ease by public transport:
Unknown