I believe I read somewhere that this site was closed due to archeological excavations. Having visited this site years ago, I am having difficulty understanding how this would be closed. I remembering standing on a hill and envisioning the chariots, felt a little like George Patton! Just checking, as I only have 2 days in Rome and do not want to waste time. Advice?
I don't know as it's completely closed but they're doing some excavation on at least one end of it.
The Rolling Stones played a concert there in June - to hue and cry from the archeological community and concerned locals. There's a mention of the dig site in this article:
So, I'm quite sure you can still clearly see the field from the Aventine or other nearby spots but it's possible - depending on plans for the excavation - that some sections of the site itself may be blocked to foot traffic. I know your time is short but if you're interested in seeing a circus, go out to Villa of Maxentius (Villa di Massenzio) on Via Appia Antica. That one is 2nd in size to Circo Massimo, and while little remains, it's the most well-preserved of all Roman circuses, with more of it still visible.
There are fences around it and signs about what is going on. You can look down on it.