The activists sat on the steps of the Acropolis Museum, with some holding rainbow flags, while others held a banner reading "Homophobia is not in the Olympic Spirit" and "Love is not Propaganda."
Police presence was light and there were no incidents.
The official handover ceremony will take place later Saturday.
The 22nd Winter Olympics are scheduled to take place Feb. 7-23 in Sochi. Some 2,800 athletes from more than 80 countries are due to compete.