How many visitors, international and domestic, visit the place where three of the state's four largest incorporated cities are located?
Nevada:  Nearly three-quarters of Nevada's people live in Clark County, which contains the Las Vegas–Paradise metropolitan area where three of the state's four largest incorporated cities are located. Las Vegas–Paradise, NV MSA:  The metropolitan area is one of the top tourist destinations in the world, drawing over 40 million international and domestic visitors in 2013 with a GMP of US$103.3 billion.
40 million