The very best place to have sex is in the back of my completely restored 1962 Lincoln Continenal Convertible, with the top down, on a hot sunny day up in the Ruby Range southeast of Elko. Plenty for room in the back seat for a handball court. The smell of leather is an added aphrodisiac. And the sweat wipes clean without damaging the upholstery. It's a wonderful car.
Second best place is in my Jeep Wrangler ragtop (with ragtop down, of course) at about 10,000 feet in elevation with the cancer beating sun hitting us. There's lots of different positions one can enjoy in a Wrangler without a ragtop. Especially if you have the over the roll-bar sound bar speakers.