Mesa Verde National Park, Colorado
Located in southwestern Colorado, Mesa Verde National Park is open all year long, but it's a vastly different experience once the snow falls. In January, the average high temperature is just 40 degrees F (4 degrees Celsius), and once the sun sets, lows are in the 20s. Snow isn't uncommon and it can close roads or make them treacherous for driving. Provided it's open, the Mesa Top Loop Road provides access to a variety of historical attractions and trails [source: Repanshek].
The park is renowned for its huge array of primitive cliff dwellings and architectural sites in the Rocky Mountains. Visitors can catch glimpses of elaborate homes built into the steep cliffs from prehistoric times. However, the only dwelling normally open for tours in winter (Spruce Tree House) has been closed for the foreseeable future due to safety concerns about falling rocks. Nevertheless, you can still glimpse it from overlooks near the Chapin Mesa Archeological Museum, which is also open year-round and houses many prehistoric artifacts [source: NPS].
In the winter, visitors, can get their fill of cross-country skiing, snowshoeing and other winter sports. There are even ranger-guided winter ecology hikes for people who are interested in the local environment.