Interstate 610 (abbreviated I-610) is a freeway that forms a 38-mile-long (61 km) loop around the downtown sector of city of Houston, Texas. Interstate 610, colloquially known as The Loop, Loop 610, The Inner Loop, or just 610, traditionally marks the border between the inner city of Houston ("inside the Loop") and its surrounding areas. It is the inner of the three Houston beltways, the other two being Beltway 8 (Sam Houston Tollway) and State Highway 99 (Grand Parkway), of which various segments are under construction or planning. It is one of four interstate loops not to share its route with another interstate freeway, the others being I-270, I-295, and I-485.