Austin, Texas is 11 times larger than Round Rock, Texas.
Area: 933 km2 calculated
Austin is the capital of Texas and the seat of Travis County. Located in Central Texas and the American Southwest, it is the 11th-most populous city in the United States of America and the fourth-most populous city in the state of Texas. Wikipedia
Area: 88 km2 calculated
Round Rock is a city in the state of Texas within the Greater Austin, Texas metropolitan area and Williamson County. The 2013 census estimate places the population at 109,821. Wikipedia