Here are some that may not have been mentioned yet, in no particular order:
Monarch butterfly reserve in southern Michoacan state in Mexico. Millions of butterflies flitting around in a meadow near the top of a mountain. This was about 15 years ago when the butterflies were very plentiful.
las Pozas surreal sculpture garden set in a lush tropical forest near Xilitla, San Luis Potosi state, Mexico. Bizarre but beautiful.
looking into the caldera from the rim of the active Villarica volcano, near Pucon, Chile (in retrospect, this was dangerous, even though I hiked up in a small group with a guide, as required). Little eruptions were constantly happening inside the caldera.
Sigiriya, an astounding enormous 200 meter (660 ft) high rectangular rock in Sri Lanka. You walk up over 1,200 steps (including a few metal spiral staircases attached to the side of the rock with nothing beneath you).
snorkeling in the Red Sea. The vast array of colorful fish in large numbers amazed me
the gorgeous Na Pali coast on the Island of Kauai
Waimea Canyon on Kauai
The view at the end of the easy
Sentinel Dome hike in Yosemite (similar to views at nearby Glacier Point), esp. in late spring when the waterfalls in Yosemite Valley have vast amounts of water.
Giant Forest section of Sequoia National Park, the largest concentration of giant sequoia trees that exists.
Stunning main reading room at the Library of Congress
First glimpse of
Spider Rock in Canyon de Chelly
Incredible variety of cacti in several Mexican deserts (far more cactus species are native to Mexico than anywhere else), including
Tehuacán-Cuicatlán Biosphere Reserve, and deserts between Zacatecas & San Luis Potosi.
Mount Rainier when it's first visible (viewed both on the ground as well as from an airplane)
the extensive and varied Huntington Gardens in Southern California
Art deco architecture in Napier, New Zealand
British colonial architecture in Penang, Malaysia.
Moki dugway road in southern Utah near Monument valley
Places which I think have been mentioned by others: Redwood National Park (more impressive than Muir Woods, which is itself impressive), Crater Lake, Yellowstone, Venice, statue of David, Eiffel Tower, 2017 total solar eclipse, Bristlecone Pine forest in eastern California at 10,000 ft (much more impressive and healthy trees than 2 other Bristlecone pine forests I've seen in 2 national parks), Bryce Canyon. eta: the mezquita in Cordoba, Spain. I was not prepared for its beauty and immense size.