The oldest complete building in Ireland and the first to use mortar, 13th-century Reginald's Tower is an outstanding example of medieval architecture. The city's key fortification, its 3m- to 4m-thick walls were built on the site of a Viking wooden tower. Over the years, the building served as an arsenal, a prison and a mint; it now houses a museum recording the city's Viking and early medieval history. The sparse exhibits include the tiny but exquisite Waterford Kite Brooch , made around 1100.
