At nearly 80 square miles, this national park (one of six in Ireland) is well known for its rare species of plants and animals, nature trails for walking and hiking, and water so fresh it’s considered a key ingredient in the centuries-old recipe for Guinness. For sensational scenery, try the R756 road from Dublin, which passes through the Wicklow Gap—one of only two routes crossing the Wicklow Mountains from east to west—or take the R115 along the spine of the mountains, which passes from…