Dubai, United Arab Emirates
On my way to India from Boston, and on my way back to Boston from Sri Lanka, I had 8 and 12 hour layovers respectively in Dubai. Both overnight, that left about 2-4 hours each night to do something in the city before attempting to sleep on a chair in the airport. (Not pleasant.)
Shoutout to my friend Abhishek, who gave me some great tips! …which due to my own fault, I was unable to follow.