Garden of the Gods (GOTG from here on out) is a public park funded by Colorado Springs and the proceeds from its own gift shop, but it entirely free if all you want to do is visit and wander the park. There's a paved drive that you can take if you're just in the mood to pass through, but you can also bike or hike a number of various paths around the park. If I lived in the area, I believe it would be a constant weekend outing for me. It was designated as a National Natural Landmark in 1971.
The rock formations at GOTG were created by an upheaval along a natural fault during the uplift of the Rocky Mountains. Native Americans considered it a sacred place, unsurprisingly, and the Ute's, in particular, incorporated it into their creation stories. Early Spanish and other European explorers began visiting the area in the 16th century. The public park was created when Charles Eliott Perkins donated 480 acres of land containing part of GOTG to the city in 1909, and William Jackson Palmer later donated his Rock Ledge Ranch which contained the remaining formations.
The primarily sedimentary beds of red, pink and white sandstones were eroded during the Pleistocene Ice Age into the present forms, including "Balanced Rock", a fascinating formation that is now, stabilized in place by concrete lest it move and crush the adoring public around it. Although it is unlikely to topple over without a major earthquake, I was still a bit nervous driving between these two pillars.
Although the park is free, don't overlook the very excellent Visitor and Nature Center across from the park entrance. The center contains many well-done and informative displays about the parks formation, ecology, and history and offers some excellent scenic views for family photos.