Spoiler (click to reveal)
The card reads (translated from Dutch):
When a player uses the action on card 6 (over the border, where you can build outside the chosen regions for €5 extra), he may put a neutral playing piece on max 2 fields "15" to block it for other players.
Do you put down 2 pieces in any city every time you use that action? Or must you put the neutral piece on the city where you build and can every player use the action from card 11(this card) twice? Or can this card be used twice ever (so in the end there are a maximum of 2 neutral player pieces on the board)?