  We prove large-time Gaussian upper bounds for continuous-time heat kernels of
Laplacians on graphs with unbounded geometry. Our estimates hold for centers of
large balls satisfying a Sobolev inequality and volume doubling. Distances are
measured with respect to an intrinsic metric with finite distance balls and
finite jump size. The Gaussian decay is given by Davies' function which is
natural and sharp in the graph setting. Furthermore, we find a new polynomial
correction term which does not blow up at zero. Although our main focus is
unbounded Laplacians, the results are new even for the normalized Laplacian. In
the case of unbounded vertex degree or degenerating measure, the estimates are
affected by new error terms reflecting the unboundedness of the geometry.
