Great Sand Dunes National Park
Location: The best way I can tell you how to get there is to advise you to google it ;) Since this is a National Park, it's its own location. The closest city looks to be Alamosa, CO. Google maps is your friend - it will direct you wisely. (Pssst. The drive is about 3.5 hours from Denver, if that gives you any context).
Elevation/distance: Great Sand Dunes National Park is home to the tallest sand dunes in the country. The "dune-park" is 30 square miles, and there is no trail. You can make this one as short or as long as you like. The highest dune is 750 feet, but don't forget you are sitting at over 8,000 feet in elevation just being there.
Description: The sights here are absolutely unreal. Growing up close to the dunes of Lake Michigan, I was skeptical. You've seen one dune, you've seen it all... right?
You get out of your car, and suddenly you are surrounded by the Sahara Desert, only in Colorado. Look to your left and you'll see snowcapped mountains. Look to your right? Miles upon miles of sand-scrapers in all their glory. The whole time we were there, I kept telling Cal "I can't believe this is real!"
This is absolutely worth the drive, in my opinion. I've truly never seen anything like it.
Who I would recommend it to: EVERYONE. It doesn't matter your level of physical activity or if you are used to the elevation gain of Colorado yet. It's magical even if you don't hike to the top (although we did). If you do choose to take the trek to the top, the hike isn't bad. Since there is no trail, I can't say exactly how far we went, but I'm guessing 4-5 miles. The sand is decently packed, so it's not your normal "beach-like" experience. You could also climb one small dune at the beginning, and still be in awe. You could not climb any dunes and be in heaven. It's breathtaking. Take the trip. It's worth it!