Cronk ny Merriu ('hill of the dead') is an Iron Age promontory fort overlooking Port Grenaugh near Santon, first defended by a timber stockade and later rebuilt with an earthen rampart, ditch, and raised timber walkway. Norse settlers later reused the site, building a rectangular longhouse as part of a coastal lookout network; excavation in 1950-52 found little evidence of everyday domestic life, suggesting it served primarily a defensive or watch function. No dating evidence was recovered for the longhouse itself, though a halfpenny of Edward I (1280-81) found in the backfill suggests activity continuing after Norse rule ended in 1265. The Norse building's design informed reconstructions at the House of Manannan museum in Peel.