Grand Canyon. Once seeing it in person. The second time seeing it was on a flight to San Diego as we were flying over it at sunset. If the flight had been on time, we would have not seen it at sunset on a crystal clear night. Instead we were about 2 1/2 hours late and what a surprise.
@billybob : I have flown over it too. It is an amazing sight! Flying over Bryce and Zion National Parks is great too. Unfortunately, I have not been to any of the three on the ground.
Devil's Tower, Wyoming made the biggest impression on me.
@RambleOn : Before or after seeing Close Encounters ? Haven't been there in person, but would be a spot to see. We took a helicopter ride over and in the Grand Canyon and would certainly vote for it.
@mypeez : Before! I have never seen Close Encounters. I was in high school when we made the trip that included Yellowstone and Devil's Tower. That's how strong the impression was.
I've had a hard time coming up with an answer; maybe I'm trying too hard. So I have the Arches National Park under the stars, the Appalachian Mountains in North Carolina during a misty sunset, and this ...
Take me back, take me way, way, way back On Hyndford Street Where you could feel the silence at half past eleven On long summer nights As the wireless played Radio Luxembourg And the voices whispered across Beechie River In the quietness as we sank into restful slumber in the silence And carried on dreaming, in God And walks up Cherry Valley from North Road Bridge, railway line On sunny summer afternoons Picking apples from the side of the tracks That spilled over from the gardens of the houses on Cyprus Avenue Watching the moth catcher working the floodlights in the evenings And meeting down by the pylons Playing round Mrs. Kelly's lamp Going out to Holywood on the bus And walking from the end of the lines to the seaside Stopping at Fusco's for ice cream In the days before rock 'n' roll Hyndford Street, Abetta Parade Orangefield, St. Donard's Church Sunday six-bells, and in between the silence there was conversation And laughter, and music and singing, and shivers up the back of the neck And tuning in to Luxembourg late at night And jazz and blues records during the day Also Debussy on the third program Early mornings when contemplation was best Going up the Castlereagh hills And the cregagh glens in summer and coming back To Hyndford Street, feeling wondrous and lit up inside With a sense of everlasting life And reading Mr. Jelly Roll and Big Bill Broonzy And "Really The Blues" by "Mezz" Mezzrow And "Dharma Bums" by Jack Kerouac Over and over again And voices echoing late at night over Beechie River And it's always being now, and it's always being now It's always now Can you feel the silence? On Hyndford Street where you could feel the silence At half past eleven on long summer nights As the wireless played Radio Luxembourg And the voices whispered across Beechie River And in the quietness we sank into restful slumber in silence And carried on dreaming in God.
My wife and I were in Rapid City SD last summer and drove over to devils tower "just cuz we're close". It's easy to see why native Americans consider it sacred. It's special.
Unusual … probably Craters of the moon national monument.
From the parks website " Craters of the Moon is a vast ocean of lava flows with scattered islands of cinder cones and sagebrush. We invite you to explore this "weird and scenic landscape" where yesterday's volcanic events are likely to continue tomorrow."