Gion Matsuri is one of the, if not the most, famous festivals in Japan. It actually lasts pretty much the the whole month of June but the peak of the festival is July 17th with the Yama Hoko Parade. This is a massive parade where 32 floats are either pulled or carried throughout downtown Kyoto. More massive than the parade itself is the crowds of people that come to watch it. Seriously, if you are not good with crowds, then you might wanna pass on this festival. I was once told that there is an old Japanese joke that goes:
What did you see at Gion Matsuri?