Spring Mountain (race track about an hour north of Vegas) is expanding, and will now be the worlds longest, setting the ring to 2nd. The Nürburgring is 13.1 mile, but the expansion will make Spring Mountain more than 15 miles

John Morris bought the burgeoning Spring Mountain Motorsports Ranch racetrack in 2004 and recently paid $5 million for an adjoining property to accomplish an ambitious plan: building the world’s longest professional racetrack.

Morris is also planning for a 6-mile off-road desert course for trucks and ATVs and a racing track for high performance go-karts as well as a 6,000 foot drag race track that will double as an aircraft landing strip.

Spring Mountain has a racing school there that teaches with Corvettes or Camaros, and was the location for a couple of the Optima Ultimate Street Car finals.

http://www.digitaltrends.com/cars/spring-mountain-racetrack/