The player holding the Free city card play's its card followed by their own card.
Rules for the Free city:
The Free city can buy resources from its two neighboring cities according to the normal rules. If a resources is available from both neighboring cities, the player controlling the Free city decides where it buys from (no matter the cost).
If the card chosen for the Free city can benefit from a free construction, it must be performed.
During the sixth turn of Age, the last card remaining in the Free city's draw pile is discarded at the same time the players discard theirs.