Geologically, a predominant feature of the substrata of Manhattan is that the underlying bedrock base of the island rises considerably closer to the surface near Midtown Manhattan, dips down lower between 29th Street and Canal Street, then rises toward the surface again in Lower Manhattan. It has been widely believed that the depth to bedrock was the primary underlying reason for the clustering of skyscrapers in the Midtown and Financial District areas, and their absence over the intervening territory between these two areas. However, research has shown that economic factors played a bigger part in the locations of these skyscrapers.