This photograph shows just a very small part of a very attractive hand-painted tiled wall at Adelaide zoo. But our interest here is in the white grid or lattice. In fact, it is not the lines which are of most interest here but the grid of intersection lattice points. These points are associated with many interesting problems. For example, the area of a lattice polygon (a polygon with vertices at the lattice points) is determined by a formula involving just the interior and boundary lattice points. If the polygon is convex, then there is an inequality relating the boundary and interior points.
