Question: How many visitors, international and domestic, visit the place where three of the state's four largest incorporated cities are located?

Blackford County is located in the east central portion of the U.S. state of Indiana.  The county is named for Judge Isaac Blackford, who was the first speaker of the Indiana General Assembly and a long-time chief justice of the Indiana Supreme Court.  Created in 1838, Blackford County is divided into four townships, and its county seat is Hartford City.  Two incorporated cities and one incorporated town are located within the county.  The county is also the site of numerous unincorporated communities and ghost towns. Occupying only 165.58 sqmi , Blackford County is the fourth smallest county in Indiana.  As of the 2010 census, the county's population is 12,766 people in 5,236 households.  Based on population, the county is the 8th smallest county of the 92 in Indiana.  Although no interstate highways are located in Blackford County, three Indiana state roads cross the county, and an additional state road is located along the county's southeast border.  The county has two railroad lines.  A north–south route crosses the county, and intersects with a second railroad line that connects Hartford City with communities to the west. <SEP> Rockville is a U.S. city located in the central region of Montgomery County, Maryland.  It is the county seat and is a major incorporated city of Montgomery County and forms part of the Baltimore–Washington metropolitan area.  The 2010 census tabulated Rockville's population at 61,209, making it the third largest incorporated city in Maryland, behind Baltimore and Frederick.  Rockville is the largest incorporated city in Montgomery County, Maryland, although the nearby census-designated place of Germantown is more populous. <SEP> Nevada (Spanish for "snowy"; see pronunciations) is a state in the Western, Mountain West, and Southwestern regions of the United States of America.  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.  Nevada is the 7th most extensive, the 34th most populous, but the 9th least densely populated of the 50 United States.  Nevada's capital is Carson City.  Nevada is officially known as the "Silver State" because of the importance of silver to its history and economy.  It is also known as the "Battle Born State", because it achieved statehood during the Civil War (the words "Battle Born" also appear on the state flag); as the "Sagebrush State", for the native plant of the same name; and as the "Sage-hen State".  Nevada borders Oregon to the northwest, Idaho to the northeast, California to the west, Arizona to the southeast and Utah to the east. <SEP> The Las Vegas–Paradise, NV MSA, also known as the Las Vegas–Henderson–Paradise, NV Metropolitan Statistical Area (2013), is in the southern part of the U.S. state of Nevada, coextensive since 2003 with Clark County, Nevada.  A central part of the metropolitan area is the Las Vegas Valley, a 600 sqmi basin that includes the metropolitan area's largest city, Las Vegas as well as the other primary city, Paradise, Nevada.  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.  The area contains the largest concentration of people in the state.  Cities in the metropolitan area include Las Vegas, Henderson, North Las Vegas, and Boulder City.