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 draw 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.