San Gimignano is a walled medieval hill top city with a number of high towers built by patricians. It is a very relaxing city.
It has excellent restaurants and terraces on which to enjoy people watching while having a drink.
This is an amazing town. We loved just walking the streets and discovering different parts of the town.
It is extremely beautiful and well worth visiting. We would recommend staying in the town as it gets very busy during the day. This way you can explore early in the morning and latter a In the afternoon. I would rate it more highly than Siena and Florence but I am sure others will have a different view.