The pleasure dome refers to Coleridge's poem Kubla Khan. As he says, it is a beautiful place that is surrounded by rough landscape. Imagine an oasis in the middle of a desert, except the oasis is more beautiful and the desert is much worse. It is found in the mystical land of Xanadu and is the home-place of Kubla Khan.
The basket atop the man's head in the back of the image. A lot of the lines pull toward that area, implying the center point.
Answer:
It simply means a piece of literature or art.
Another meaning is the "structure" of something.
