Rising out of the surrounding lush, flat landscape are the pretty pastel-colored turrets of the 12th-century Kalmar Castle. In 1397, the Kalmar Union was signed here—a treaty that brought Sweden, Norway and Denmark together under a single monarchy. In 1592, the medieval castle was redesigned and converted to its current Renaissance style. Take a ghost tour through the halls and dungeons, and don’t miss the permanent historic exhibits.