While visiting Nashville for a concert on August 25th, I scheduled an Uber ride at the quoted rate (iPhone app) of $21. Xx. We traveled from 5th avenue, not far from Bridgestone Arena to the Gaylord Hotel. Upon arrival, I tipped the driver in cash, and we exited the vehicle. A few seconds later, I received a notification that I had been charged $79.72! Uber informed me that there was a "surge charge" (which I had never heard of) and that it is applicable, essentially when there are very few drivers available, relative to the number of riders needing rides. Supposedly, the rider is notified of the surge charge before accepting or rejecting the ride, but I wasn't. I was simply told "$21. Xx", then charged $79.72.