Clockwork Fortress and Cave Market are a set of two promotional cards for the 1st edition of City of Iron. These cards are added to the "E" buildings; that is, they are available to build from the start of the game. The Cave Market adds one coin to your income for each different type of good you own. The Clockwork Fortress allows you to change the order of your citizen and military decks each time you refresh that deck. These cards may also be used with the 2nd edition of City of Iron, where they are placed above the usual row of buildings and are not removed until they are purchased.