There have been lots of places that have impressed me. Niagara Falls and the Grand Canyon are both spectacular. Flying over the Sahara Desert was pretty impressive, the biggest damned bunker I have ever seen. Just the sheer size and emptiness of the place. Ayers Rock was worth seeing as was flying over the Great Barrier Reef. I don't know if you can call the Pyramids and the Sphynx natural places but I'm glad that I saw them and they had a spectacular light show.
What gets me is some of the places I could have gone but didn't for one reason or another.
Yellowstone: I worked in Wyoming for a couple of years and never made it there. I wasn't too interested in going during high summer when it's awash with tourists but I had a couple of friends who wanted to take me in there during the winter on snowmobiles through the "back door". I didn't do it because I knew the park service "frowned" on the practice but I should have gone in late spring or early fall. Maybe I can still make it.
Angel Falls, Venezuela: I was all set to take a helicopter ride to see the falls and spend the week-end at a lodge there until my boss called me back to work in Caracas because he felt "exposed" without me being there. I never got a second chance.
Machu Picchu, Peru: Again not a "natural place" but a "wanta see" in my book. I had passed through Cuzco in the high Andes several times and had it arranged on one of my trips to take the Inca Highway from Cuzco to Machu Picchu. It could have been the altitude of 10,000 feet but more likely was the local beer and food the night before but I got sick as a dog and didn't make it. There is an upside to this story though. The two guys I had arranged to go with got robbed on the way. So, although I spent 3 days sitting on the crapper and honking into the wash hand basin, at least I returned to Lima with my wallet, credit cards and watch.