I just came across a thread in the national forum asking this question and thought I'd pose the same question here locally. This could be both rw and hobby world.
To start it off and what I answered in that national thread:
Inside the giant heart at the Franklin Institute Science museum was by far the weirdest place I ever had sex. It was a warm May weekday in 1998 and my girlfriend and I took advantage of a moment right then and there. We went at it for a good 5 minutes until we began to hear the next round of field trip kids coming. She got off but I unfortunately did not but she took care of that with some road head through the streets of Philadelphia in my old Jeep wrangler with the top off at the time. Exciting to say the least.