We saw many of the main tourist sites--the Forbidden City, the Summer Palace, and the Great Wall. But we loved the hutongs best--they are traditional residential alleys. They are lined with traditional courtyard residences, some of which people still live in, and some which have been converted into restaurants, businesses, and hotels.
The subways made getting around Beijing easy (and they were also very clean too!), though we also took some buses and some taxis (luckily William speaks Mandarin).
Hutong Hotels (Courtyard 7, a hotel that we stayed at which is located in a renovated Hutong. It was really nice.)
798 Arts District