In the organizer's words:

The flea market at the St. Georg city festival: this is the flea market at what is probably Hamburg's most colorful city festival! In the immediate vicinity of Hamburg Central Station, connected to the St. Georg City Festival on the lively Lange Reihe, the flea market at the St. Georg City Festival always takes place on the last full weekend in May. A great opportunity for a lively, colorful flea market experience.

Stall locations at: https://www.marktlust.de/