It is the law, that art MUST be included in Federal buildings.
Yes, a certain percentage of the total cost. At the SeaTac airport they added a runway. On one of the huge new retaining walls there is a relief sculpture on all of the panels of the walls. Estimated at $1 million dollars. Oh - the artwork is in the secure area of the airport alongside a maintenance road far from the terminal or where planes might see it. It can be glimpsed by the public on side roads if you know where to peek between the bushes and chainlink fence 130 yards away.
http://www.seattletimes.com/seattle-news/art-as-a-symbol-of-port-waste/