The Tenderloin is a neighborhood in downtown San Francisco, California, in the flatlands on the southern slope of Nob Hill, situated between the Union Square shopping district to the northeast and the Civic Center office district to the southwest. It encompasses about 50 square blocks, is a large wedge / triangle in shape (point faces East). It is historically bounded on the north by Geary Street, on the east by Mason Street, on the south by Market Street and on the west by Van Ness Avenue. The northern boundary with Lower Nob Hill historically has been set at Geary Street.

Answer this question based on the passage: what is the tenderloin district of san francisco? Let's have some stream of consciousness first.
The relevant information is: The Tenderloin is a neighborhood in downtown San Francisco, California, in the flatlands on the southern slope of Nob Hill, situated between the Union Square shopping district to the northeast and the Civic Center office district to the southwest. So, the answer is a neighborhood in downtown San Francisco , California , in the flatlands on the southern slope of Nob Hill , situated between the Union Square shopping district to the northeast and the Civic Center office district to the southwest.