I went for the first time in Siena last summer, just in the days before the Palio. I arrived in the end of June, some days before the first Palio of the year, which is traditionally held on July 2nd and repeated on August 16th. Siena is one of the most suggestive Italian cities I visited.
I remember a couple of wonderful days passed in this extraordinary city, wandering in Piazza del Campo with the sun fading on the surrounding medieval buildings. Piazza del Campo is characterized by a slope giving it an unusual depth, and walking in the square full of people lying in the sun (even if lying in the square is actually forbidden) is a really curious experience.
For those who have the will, trying the climb to the 400th step of the Torre del Mangia is a challenge to make: you can not miss it when you arrive in the square. Over the phisycal effort, if you want to get in the Tower you have also to be ready to spend: the entrance ticket costs about 7 Euros, a bit expensive even if the view from the top is very suggestive!
The square is populated by children, students, mature couples and tourists who can sit or lie down on the bricks of the study center for excellence in Siena. In summer through the narrow streets surrounding Piazza del Campo you can recover from the heat while enjoying one of the many flavors of ice cream you can taste in Siena: really charming place, which help the soul be quiet and lighter.
When I visited Piazza del Campo Wi-fi Internet connection was available in the square for free, a perfect incentive if you want to find a place where to work, study or just relax in the sunshine, especially during summer.