A diagonal line from the end of the Brooklyn Bridge (on the middle left in this picture), to the far corner of the dock on the bottom right, is a distance of 1.2 miles.
The yacht harbor closest to the WTC is about .1 mile square.
As you look at the picture, recall that the towers were about .36 miles high. Imagine the damage if they had fallen over, rather than collapsing straight down.
The NY Times had a map of the destroyed buildings, including all in 7 in the WTC, as well as several on adjoining blocks. Just heard that a tiny Orthodox church, with icons donated by Czar Nicholas II and housed in a building dating to the early 1800's, was destroyed.