Hrm. Either in the snow, underneath a couple of pine trees, on a golf-course while cross-country ski-ers were going by, or underneath the swimming pool of the same ski resort.
Yes, underneath. Not very exotic, per se.
Yar, I was spoiled for for choice my first time; not only was it in his mom’s bed <who was working in another part of the state> but as I came out in her bathrobe <he insisted>…yep, guess who walked in the front door.
She was remarkably calm about the whole thing.
Since it was only the 2nd most dramatic thing that had happened to me in the last 3 hours, so was I. 
The stock room of a goodwill. Not so exotic, I know, but different nonetheless.
On top of a huge slab of sandstone, at sunset, in Arches National Park. (with someone I had met the day before)
Exhibit floor of the National Museum of Natural History (the Smithsonian).
Different biomes of the Biosphere 2 habitat.
In a Beechcraft Bonanza (it had an autopilot).
We were at 8000 ft. It had curtains on the side windows. She insisted on closing them.
If we count oral, then washington Metro (red line).
Mose exotic was in a hammock slung between palm trees, on the beach in Jamaica.
Bali? Kathmandu? Phnom Penh? The list is extensive.
By that metric, Parker, Colorado.
Outdoors
Wing a of the science building in college.
Of course, if we’re narrowing it down to even more specific, in my wild and crazy youth there was the deserted guard booth. 3am on an outdoor stairway leading up to the second floor of a small shopping area. Pool table. Barstool.
Ah, those were the days.
Penthouse Forum has nothing on this place!
OK, I did promise to cross-post here if a thread was started (should have just started it myself), so, here it is, for your amusement:
Since our tenth wedding anniversary is coming up (and we haven’t had much more exciting things to top that one), I’m tempted to recreate that and “do the Moosomin” again.
South Beach, Martha’s Vineyard, at night comes to mind. It’s very dark there. And windy. Lotsa sand, too. Imagine that. But it was still fun.
By that metric, Parker, Colorado.
Outdoors
Wing a of the science building in college.
Attic of the Johnstown (PA) Flood Museum. A few vehicles; at least once while driving. Otherwise, mostly in rooms with comfy furniture.
Tabacon hot springs in Costa Rica on my honeymoon.
On the corner of 14th Street and 9th Avenue, in Manhattan. And I do mean right on the corner, on the curb, at night, with pedestrians and cars going by. I had had a few beers (and normally I don’t drink), the other guy had a whole lot more, and suddenly he went down on me.
Also: in the back of a Pepperidge Farm Truck, parked in front of Bloomingdale’s, in the middle of the day. I remember baked goods falling on us.
In Kentucky and Virginia…at the same time.
(camping at Cumberland Gap)
Pepperidge Farm remembers 
I hope someone understands my joke.
In the median on the East-West Expressway/State Road 408 in East Orlando, Florida. Just to the right of the location marker here. Not in a car either.