On the west side steps leading up to the Arch in St. Louis. Therefore I can lay claim to fucking under the Arch. 😉 And in a cemetery on a gravestone. When she got up you could read a portion of the epitaph on her ass.

In an elevator. Also at a party poolside trying to hide but a few people did watch and it felt good being watched while fucking.

In a the restroom of a church.

My wife and I had sex on the top of a hill full of heather. It wasn't until later I noticed a plane had flown overhead

In a life guard stand at night on waikiki beach in Hawaii.
Behind the snack bar at Buffalo Chip at the Sturgis motorcycle rally.
In the alley behind a bar.
Bent a chick over my motorcycle at a rest area one night.
Behind a tree at a backyard party.
Should I go on?

In a cemetery!

In the sauna of a big downtown hotel. The maintenance guy opened the door, saw what was going on then closed it without saying a word. Twenty minutes later my wife and I got on the elevator to go back to our room and he got on with us. Not a word.

I can think of a few. In an empty Pepsi booth at a motorcycle race with 100s of people right outside. In high school I did it standing up in the music room up against the wall behind heavy curtains used for sound deadening with a girl i was in history class with. It was actually her idea. By the way the class was empty at the time. We also did it once in there parents game room. She bent over the pool table and we went at it with her dad in the next room

I've never had sex I jerked off in a bathroom once, no one else was there but I cum in the toilet and flushed it. No one ever knew

I've had it in a few unusual places.. in a mining quarry, in an elevator, in a bus shelter in the middle of town but that's probably not that unusual these days!
My favourite was at an old job in a supermarket. The security guard was fucking the checkout supervisor in the baby change toilet, a stock cupboard in the warehouse, and in the CCTV office Perk of the job to say the least!

On top of a well in a city park