Really hard to narrow it down to 3 but if I have to-
1 Galapagos-swimming in a shoal of fish with the blue footed coughies collecting their food all around you,swimming eye to goggles with a juvenile sea lion,blue footed coughies and gannets doing their mating rituals at your feet.
2-Antarctica-just incredible.The ice,the penguins and being in Mawson's hut-fewer people have been there than the the number on the summit of Everest.
3-kayaking the Inside Passage,Alaska.Eye to eye with a humpback,humpbacks starting to bubble feed less than 100 metres away,the quiet broken only by whale songs,watching a bald headed eagle demonstrating how much better a fish gatherer it is compared to yourself.
But honorable mentions to Easter Island,Macquarie Island,Svalbad,NYC,Grand canyon,Niagara falls,Yosemite,the Badlands,Kremlin,Helsinki,The Mekong,Amazon etc,etc,etc.
To visit-1-African Game park
2-Iceland.
3-Churchill,Canada.