The Garden District is definitely one of the most beautiful and historically significant neighborhoods in New Orleans, as it was designated a National Historic Landmark. Several well-preserved southern mansions can be found in this area, so any travelers to the city should definitely take a walk around this district.
Most of the mansions were built in the 19th century, when the city first achieved real prosperity. Though originally there were only a couple of mansions on each block, so they could each have vast gardens surrounding the main dwellings (hence the name of the district), eventually the area became more urban and the lots had to be subdivided.
Now, most of the mansions are surrounded by Victorian houses, and are quite interesting architecturally to observe.
If you're going to visit the Garden District, make sure to stop by the Commander's Palace, one of the most famous restaurants in New Orleans, frequented by tourists and locals alike.