Three different "city" tiles, which produce and accumulate resources (these are not removed during clean up): either location cards, workers or ammunition. Cities are considered shared grounds, multiple players can make a deal with them, in which case, they get in each production phase the given resources. One player can also raze a city, in which case s(he) receives all accumulated resources and the city tile is removed from the game. Was initially part of the 2016 released pre-order promos for 51st State Master Set, but released separately in the webshop later on. Rules do not come in printed form, but have to be looked up on the Portal website.