Ok ManMadeMound, here is my two cents.
The two previous posts gave you a good idea of what the neighborhoods have to offer, but not of how they are laid out.
Shadyside. This is the only section of the city that has large wood frame Victorian houses (Painted Lady types). The houses have porches, and small yards. They are built quite closely together, as is the norm in Pittsburgh. The western half of Shadyside is very high end, with many mansions and very large houses.
Squirrel Hill is very similar to Shadyside, except that it was built up 20-30 years later, and reflects the architectural styles of the early 20th Century, rather than the late 19th. This is also the heart of Jewish Pittsburgh. It is decidedly less trendy than Shadyside.
South Side, is a neighborhood that is undergoing much gentrification. This was a working class area, that is now home to many college students (mostly attending Duquesne), and yuppies, along with a large population of retired long time residents. One thing the other guys failed to point out. This is a row/townhouse neighborhood. Not sure where you are from, or if you are familiar with this type of hood. There are no yards here, and the houses are stoop fronted. I feel this is neccessary to point out, because while many people love the type of density and streetlife this type of layout provides, others can't stand the concept of rowhouse living.
Oakland is the home of the University of Pittsburgh. It's crowded, dirty, rundown and overpriced, but it's vibrant as hell. Loved by some, despised by many.
The historic North Side neighborhoods have some of the best architecture in town. They are also bordered by some very rough areas. These are also rowhouse hoods.
Bloomfield is the main Little Italy. It is safe, and very quaint. It is also very densely built up. No yards or porches, your stoop and the pavement function as your yard.
Lawrenceville is the most densely built up neighborhood in the city. The vast majority of the houses are red brick rowhouses. Forget about a yard, though there are some rows that have porches.
Mt Washington is the large hill that lies south of Downtown. While the streets that have a view of Downtown are quite expensive, the rest of the neighborhood is reasonable. You will find closely built detatched houses here. Tiny front yards, with more yard in the rear is the norm. There are large numbers of both brick, and frame homes here.
Polish Hill is a very very quaint area located about a mile east of Downtown. It is very hilly, and very dense. There is a wide variety of housing types here, including quite a few flats.
There are other areas, but they are either very rough, or not as conveniently located.
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