🇮🇪 Ireland · Earthwork
Grianan of Aileach
Iron Age to Early Medieval (c.1000 BCE–1100 CE) · Iron Age Gaelic → Early Medieval Uí Néill
Donegal hilltop royal cashel (23.5 m diameter) on Greenan Mountain — northern Uí Néill kingship inauguration fort.
🇸🇪 Sweden · Earthwork
Stavgard Ringfort (Gotland)
Migration Period to Vendel Period (c.400–800 CE) · Gotlandic Iron Age
Pre-Viking ringfort (fornborg) on Gotland's southeast, circular limestone wall 80–100 m diameter enclosing 0.5 ha, with inner house terraces and Iron Age ceramics.
🇩🇰 Denmark · Hillfort
Nonnebakken Viking Ringfort (Odense)
Viking Age (c.980 CE) · Danish Viking Age
Viking ringfort beneath Odense's former castle at Nonnebakken (Nuns' Hill), 120 m diameter with 13 m wide turf rampart, discovered by C14 and magnetometry under Odinstårnet lot.