I’ve been going to Rocky Mountain National Park (RMNP) since I was a kid. My parents built a house up near the park when I was a kid and it’s been great to have a place to go that is so close. The park is a great place to visit and is a short day trip from Denver. In the winter, Trail Ridge road is closed. During the summer its open and you can make a 5 hour drive starting and ending in Denver. Estes Park sits on the east side of RMNP and Grand Lake sits on the west side. Most of my time has been spent on the west side.
There are a lot of trails to explore in the park with a few taking you above timberline, which is roughly 12,000 feet high in elevation. Many people are not used to the low oxygen at the higher levels of the park but drinking lots of water helps. Being a native of Colorado and Denver, I am fairly used to the elevation although I start to feel it around 10,000 feet. The park is also full of wildlife. You can see elk, deer, moose, and various ground animals. When you get higher up in elevation, you will see the marmots that can be found just off the road.
RMNP is worth the day trip when but can get very busy on the weekends because it is so close to Denver.