If the weather is right, a few days in the densely wooded Gauja National Park, just 20 mi/30 km northeast of Riga, can be the highlight of a trip to Latvia. Set in the Gauja River Valley, Gauja National Park has scenic Devonian sandstone cliffs, small caves and wonderfully tall, ancient oak trees. A nice way to see the park is on trail rides or—when the water levels are high in spring—by boat.
In Gauja, you'll want to stop in Cesis, a former Hanseatic town in the middle of the park. Visit St. John's Church (dating from 1281) and the Cesis Castle (founded by the Knights of the Sword in the 1200s, and more recently restored). Cesis hosts a number of popular summer festivals, including an opera festival, a beer festival and the Knight's Festival (with a jousting tournament). http://www.gnp.gov.lv/public/eng.