Claimed to be Ireland’s oldest building that’s still in day-to-day use, Reginald’s Tower was built around the year 1000 by the Viking invaders who founded the city. Today it houses a museum devoted to that period in Waterford’s history. While much of it is interpretive in nature, with plaques that tell the story in absorbing detail, a surprising number of actual items are on display too: fragments of Viking pottery, coins, and jewelry, including the stunning Waterford Kite Brooch, an ornamental clasp dating from the late 11th century, intricately patterned with fine threads of gold and silver. Be careful when climbing the old stone staircase—in order to confound attackers, these “stumble steps” were designed to be deliberately uneven, hence easy to trip over (also oriented in such a way to make wielding a sword impossible if you’re right-handed—so better leave yours behind).