One of the best ways to see Cambridge is by punting along the River Cam. There are a number of boatyards along the river from which punts can be hired - either with a 'chauffeur' or without. Although slightly more expensive, if you haven't been punting before, you should go for the chauffeured option if you don't want to end up in the water.
In just over an hour, you can make your way past all of the riverside colleges, starting with Magdelane and ending with Queen's. It's an excellent way to see some of the best (and worst) architecture in Cambridge, including the famous library at Trinity College, the chapel at King's College, and the 'Mathematical Bridge' that joins the two halves of Queen's College.
It's an excellent way to spend a sunny, summer afternoon.
Scudamore's Boatyard is one of the main companies that hires out punts in one-hour time slots. They are located near Magdelane Bridge and also next to the Anchor pub on Silver Street