In this picture the buildings and the sky interact to create an almost abstract image of geometric shapes. the key shape is that of the sky. A slow shutter speed was probably used alone with some serious dodging to achieve the tone and blur in the clouds. A wide angle lens was probably necessary to get a view that includes so much of the buildings on each side. Though it looks almost HDR, I would guess that it is just a lot of dodging and burning based on the light on the edges of the buildings.