  America's first urban centres were allegedly located at the Supe Valley sites
in Peru. After investigating the location and the orientation of the main built
structures, we show that it is not only the presence of the River Supe that
determines their orientation but also astronomical relationships within the
orientation of the buildings dictate their setting within the valley. The
southernmost position of moonrise on the horizon seems to be the most important
astronomical target. There is the possibility of an evolution toward
attributing greater importance to the June solstice sunrise and the rising of
certain stars or asterisms. These orientations could elate to specific moments
throughout the year, in particular to seasonal rains, subsequent river
flooding, and agricultural cycles. This is one of the earliest examples of the
interaction of land- and skyscapes in human cultures and indeed the first in
the Americas.
