1. Garden of the Gods and Manitou Springs
2. Overview: Venture south from Denver to encounter the surreal red rock formations of Garden of the Gods, a National Natural Landmark where towering sandstone monoliths contrast against the snow-capped peaks of Pikes Peak. Take a leisurely hike or join a guided jeep tour to fully immerse yourself in this geological wonderland. Afterward, head to Manitou Springs, a quaint town known for its healing mineral springs and vibrant arts scene.
3. Duration: Full Day
4. Start Time: 8:00 AM
5. End Time: 6:00 PM

6. Must Try: Sample the unique mineral waters from the various springs around Manitou Springs.

7. Great Sand Dunes National Park

8. Overview: Prepare for an otherworldly experience at the Great Sand Dunes, a surreal landscape of towering dunes nestled against the Sangre de Cristo Mountains. Rent a sandboard or sled and glide down the slopes, or hike Medano Creek for a serene walk between dunes and water. The park offers a stark contrast to Denver's urban setting, making it an unusual yet thrilling day out.
9. Duration: Full Day (consider early start due to distance)
10. Start Time: 6:00 AM
11. End Time: 8:00 PM

12. Must Try: Sandboarding or sledding on the dunes.

13. Marble, Colorado and Yule Marble Quarry Tour

14. Overview: Dive into history and explore the lesser-known town of Marble, nestled deep within the Elk Mountains. This tiny community was once a bustling marble mining hub, and today you can take a tour of the historic Yule Marble Quarry, which supplied the stone for the Lincoln Memorial and other iconic structures. Surrounded by pristine wilderness, Marble also offers scenic hikes and a glimpse into Colorado's mining heritage.
15. Duration: 9:00 AM to 5:00 PM
16. Start Time: 9:00 AM
17. End Time: 5:00 PM

18. Must Try: Join the guided quarry tour to learn about the extraction process and see the massive blocks of marble.

19. Estes Park and Stanley Hotel Ghost Tour

20. Overview: A scenic drive through the Rockies leads you to Estes Park, a charming mountain village that serves as the gateway to Rocky Mountain National Park. But for an unusual twist, book a ghost tour at the historic Stanley Hotel, famously known as the inspiration for Stephen King’s "The Shining". The hotel's eerie beauty and storied past make for an unforgettable evening.
21. Duration: 10:00 AM to 8:00 PM (Ghost Tour typically starts late afternoon)
22. Start Time: 10:00 AM
23. End Time: 8:00 PM
24. Must Try: Participate in the ghost tour, if you dare!

Each of these unusual day trips showcases Denver's surroundings in a distinctive light, promising experiences that are far from ordinary. Whether it's natural marvels, historical explorations, or eerie encounters, Denver's vicinity has it all for the adventurous traveler.