Beacon Hill is a 19th-century downtown Boston residential neighborhood situated directly north of the Boston Common and the Boston Public Garden. Most people think of city living as anonymous and isolating. But this cozy enclave, filled with nearly 10,000 people, is more like a village than an anonymous city. It has a rich community life, with neighbors knowing neighbors and everyone meeting on the Hill's commercial streets and at its myriad activities. Approximately one-half mile square, Beacon Hill is bounded by Beacon Street, Bowdoin Street, Cambridge Street and Storrow Drive. It is known for its beautiful doors and door surrounds, brass door knockers, decorative iron work, brick sidewalks, perpetually-burning gas lights, flowering pear trees, window boxes, and hidden gardens. Its architecture, mostly brick row houses, includes the Federal, Greek Revival and Victorian periods, as well as early 20th-century colonial revival homes and tenements. The architecture is protected by restrictive regulations that allow no changes to any visible part of a structure without the approval of an architectural commission. Beacon Hill contains a South Slope, a North Slope and a Flat of the Hill. Charles Street is the neighborhood's main street and is filled with antique shops and neighborhood services. The Massachusetts State House is at the top of the Hill overlooking Boston Common.