We introduce a family of planar regions, called Aztec diamonds, and study the ways
in which these regions can be tiled by dominoes. Our main result is a generating function
that not only gives the number of domino tilings of the Aztec diamond of order $n$ but also
provides information about the orientation of the dominoes (vertical versus horizontal) and
the accessibility of one tiling from another by means of local modifications. Several
proofs of the formula are given. The problem turns out to have connections with the
alternating sign matrices of Mills, Robbins, and Rumsey, as well as the square ice model
studied by Lieb.