Denver
Chessman Park and Botanic Gardens, nice to walk around and see the Rocky Mountains in the distance. Museum of the Unsinkable Molly Brown on Penn Street, she was an American socialite, philanthropist, and activist who became famous due to her survival in 1912 of the Titanic. Next door to it is Perk on Penn, a very nice place to have a bagel for lunch.
Mile High Club?
Don’t forget to become a member of the Mile High Club of Denver: snap a a photo of the Mile High step at the stairs of the Denver Capitol building. That is exactly 1 mile above sea level.
Golden
a cute little town just before the Rocky Mountains, hike the North Table Mountain Park. Try and see a concert at Red Rocks Amphitheater in nearby Morrison.
Boulder
Fun student town, drive up for a view of the city and continue via Canyon Drive to Boulder Creek and Boulder Falls.
Silverthorne
This town along the I70, has in the winter an Ice Castle made of icicles. A magical place to walk around when the sun is out. Close to it, in Frisco go for lunch at Butterhorn. Good food and funny decorations.
Breckenridge
Breckenridge is a great ski resort, so go here in the winter. It is about 9000 ft above sea level (almost 3 km), so drink lots of water.
Maaike: Coming from the Netherlands (partially below sea level), the owners of the B&B I was staying, were very serious about warning me to drink lots and contact them if I started to feel a headache and not good.
Fireside Inn is a fun place to stay, also in the dorm room, shared with 10 other people. When you are in Breck, you should definitely go dog sledding with Good Times Adventures (they are located at the end of Tiger Road). It is seriously lots of fun. They have boots and a snow suit for you, but bring gloves and sunglasses. Have some delicious pizza at Fatty’s, it is a very popular, crowded place, with a line waiting at the door, but it is worth the wait! At Glenwood Springs there are some great hot springs to chill while enjoying the mountains surrounding you.
Grand Junction, Colorado National Monument, a huge national park with canyons and has a beautiful scenic road along the Rim Rock Drive with amazing canyons and great views.
Colorado Springs
Garden of the Gods, lightnlense Light Painting, Manitou Springs, Seven Falls (park at hotel, free shuttle, steep stairs, nice views and work out)