"Yes, it's in the books. Also there are two wikis:http://awoiaf.westeros.orghttp://gameofthrones.wikia.com"

"As another commenter pointed out, the square tower building is not the citadel, but nor is the citadel connected to it. The tower is not just a lighthouse however, it is also a castle and the seat of House Hightower, the lords of Oldtown. The citadel and library are in the second largest building (the one with the dome) that can be seen in the image of the city, to the right of the tower."