When did the resort where UFC Fight Night: Namajunas vs. VanZant was held open?
UFC Fight Night: Namajunas vs. VanZant: UFC Fight Night: Namajunas vs. VanZant (also known as UFC Fight Night 80) was a mixed martial arts event held on December 10, 2015, at The Chelsea at The Cosmopolitan in Las Vegas, Nevada. Cosmopolitan of Las Vegas: The Cosmopolitan of Las Vegas (commonly referred to simply as The Cosmopolitan or The Cosmo) is a luxury resort casino and hotel on the Las Vegas Strip in Paradise, Nevada. Cosmopolitan of Las Vegas:  The resort opened on December 15, 2010, and is located just south of the Bellagio on the west side of Las Vegas Boulevard.
December 15, 2010