The Altstadt Grossbasel is the historic core of Basel, home to 2,749 residents on just 0.4 square kilometers, making it the 19th largest of 21 neighborhoods. It is a compact, central area, bordered only by the Vorstädte quarter and connected to Kleinbasel across the Rhine by the Mittleren Brücke and the Basel ferries.

This neighborhood is defined by its exceptionally low share of children and families. With a youth dependency ratio of 15.1, it ranks 20th out of 21 neighborhoods, meaning it has the second-lowest proportion of young people relative to its working-age population in the entire city.

Geographically, it is one of Basel's smallest districts. Its population of 2,749 is also the 19th largest. About 31.8% of residents are foreign nationals, placing it in the middle of the pack at rank 15. The population structure is notably older, with an old-age dependency ratio of 30.9, which is slightly above the city average.

Socially and economically, the Altstadt Grossbasel presents a portrait of established, affluent urban living. It has one of the lowest shares of welfare recipients in the city at just 1.8%. The neighborhood's wealth is further underscored by a high Gymnasialquote of 57.9%, indicating a highly educated population where the majority of children attend the academic Gymnasium track. The built environment is historic and dense, with an average building construction year of 1823 and a very low share of single-family homes at 9.9%. Despite this density, apartments are relatively spacious, averaging 88.1 square meters.