The present-day public space, where concerts are organised (e.g. Rolling Stones) and meetings are held, dates back to the 6th century BC. The circus was originally built as a chariot race track and was later also used for games or gladiator fights. Consequently, there were many circuses built all around the Roman Empire and they were all based on this one.
Though not much is left from the original Circus Maximus, the stroll down the public park is a very pleasant one, especially when the weather is nice. There are no admission fees and the area is open to public at all times of the day.
Free of charge.