This is the 'common area' of the Forum - where the famous words, 'Friends, Romans, Country men, lend me your ears..." was given.  Right where that tree is now was the speaking area where you could address the crowd.  It had never occurred to me before visiting the site that quote was actually literal and not just a figure of speech - friends were the Senators, Romans were the common city dwellers and the countrymen were the farmers from the outskirts of the city doing business at the Forum...