Most Expensive Buildings in the World

Hey all, being somewhat interested in civil engineering, I got to wondering what buildings cost the most money to build. Wikipedia supplies a list at the following link: https://en.wikipedia.org/wiki/List_of_most_expensive_buildings

I guessed that nuclear power plants would top the list since they involve so much redundancy and security. I was partially correct - several nuclear power plants do make it onto the top ten list. The other top spots are occupied by casinos, monster resorts, stadiums, and some hospitals. Interestingly enough, the new Apple headquarters made the list (it's estimated to cost around $5 billion to complete). The picture above is of the Marina Sands, which came in fourth place:

Leave it to gulf oil money to win the top spot though. The Arbaj Al Bait is an absolutely enormous mixed-use building in Mecca. Apparently the Saudis spared no expense in its construction because it cost $15 billion to build (three times the cost of the new Apple headquarters!). Here's a pic: