Ring of Iron
The Ring of Iron (Welsh: Cylch Haearn) or Iron Ring of Castles was a chain of fortifications and castles built across Wales at Edward I's command after the death of Llywelyn ap Gruffudd in 1282 and the subsequent Conquest of Wales by Edward I of England. Edward spent over £80,000 on all of the castles, with £20,000 being incurred just by Rhuddlan Castle, Aberystwyth Castle, Flint Castle, and Builth Castle.