World renowned from it's wealthy history originally flowing from Gold Rush, Comstock Lode and Transcontinental Railroad, Nob Hill provides great views with a dose of perspiration :)
Perched on top, Grace Cathedral, Top of the Mark and Huntington Park are easy to access (and appreciate!).
Architecture buffs may also enjoy the Flood Mansion (one of the few buildings to stand after the 1906 Fire) and Fairmont Hotel among others. SF City Guides has a good architectural and historical tour of the area.
Nob Hill was developed after the Cable Cars made the area more accessible, and is still cable-reachable from all of the lines (aka, from Downtown, Civic Center, Union Square, North Beach and Fisherman's Wharf) - and the nearby and excellent (and free!) Cable Car Museum is worth a peak as well.
Wikipedia: http://en.wikipedia.org/wiki/Nob_Hill
