Developers have proposed building the world's tallest roller coaster in Las Vegas, known as the Polercoaster. Created by US Thrill Rides, the Polercoaster is both a thrill ride and observation tower combined into one. Marketed for utilizing space to the fullest, the roller coaster that winds around the tower would stand as the tallest in the world if it opens.
However, the attraction also has to pass inspection from the FAA due to its height - claimed to be a total of 650 feet - be approved by the city, and find funding before anyone can take a ride. That also leaves the exact height of the coaster in question. The ride appears to utilize a spiral lift hill, with the station at ground level. Plenty of swoops and tight curves are found on the way back down. The center of the tower features glass elevators, and the top section could hold a restaurant and/or retail locations.
According to the news story the plans show the tower near the Tropicana, which is a great location right along the famous Strip.
You can read more about the Polercoaster from designer US Thrill Rides on their website.