Tourism in metropolitan Detroit, Michigan is a significant factor for the region's culture and for its economy, comprising nine percent of the area's two million jobs. About 15.9 million people visit Metro Detroit annually, spending an estimated $4.8 billion. Detroit is one of the largest American cities and metropolitan regions to offer casino resort hotels. Leading multi-day events throughout Metro Detroit attract super-sized crowds of hundreds of thousands to over three million people. More than fifteen million people cross the highly traveled nexus of the Ambassador Bridge and the Detroit-Windsor Tunnel annually. Detroit is at the center of an emerging Great Lakes Megalopolis. An estimated 46 million people live within a 300-mile (480 km) radius of Metro Detroit.