Nob Hill is one of those places that feels quintessentially San Franciscan-- with its steep hills, city vistas, and trolley car rolling up and down its slopes.
If you have a bit of extra cash, stay at the Fairmont, Standford, or Mark Hopkins Hotels at the top of the Hill. Each of these hotels have an interesting and unique history-- you can even see scorch marks from the 1906 Fire on the wall by the Stanford Hotel.
Be sure to check out the doors on Grace Cathedral, they are a Nazi-made replica of the doors of the Florence Bapistry next to the Duomo. Rather, they are a replica of the Nazi-made replica because the first replica was deemed to valuable to be exposed to the elements. San Francisco fog is legendary for many reasons-- architectural deterioration is one of them.