The World's Largest Sports Venue

The Indianapolis Motor Speedway is the largest sports venue in the world by seating capacity, with 257,325 permanent seats and infield space for hundreds of thousands more. On race day it becomes one of the most populous temporary cities in the world. The first Indianapolis 500 was held in 1911, won by Ray Harroun driving a single-seat car of his own design called the Marmon Wasp. Harroun also debuted one of the world's first rearview mirrors that day, an invention he added because he was racing without a riding mechanic to warn him of approaching cars.

Source: Wikipedia