Theatre of Dionysos
If I remember correctly, this theatre holds will hold up to 6000 people. I will double check that number because it sounds too big, but I remember when our guide told us, I was amazed at the number. I would have never realized it. Originally had a roof over it, but when the gun powder was stored in the temple exploded, it destroyed the roof. They say the sound is still exceptional for the theatre and is still used today during the spring and fall when it is not too hot or cold outside.
I went back and looked and could not find the seating capacity, but I know I was amazed when our tour guide told us.