Quadropolis: Monuments of the U.S. is a set of four promotional tiles for Quadropolis that can replace some of the monuments in the existing game. Monuments — which are used only in the game's expert mode — are rare buildings that earn you victory points when placed next to parks, shops, or public services in the city that you build, but cost you points when placed next to harbors or factories.
Quadropolis: Monuments of the U.S. includes the Lincoln Memorial, the Golden Gate Bridge, Independence Hall, and the "Welcome to Fabulous Las Vegas" sign. To use one of these tiles, replace the monument tile in the base game that bears the same ID number as the promo tile. (Monuments with the same ID number cannot coexist in the game, even if they have different final letters.)
For more information, visit the BGG listing.