  We study non-planar correlators in ${\cal N}=4$ super-Yang-Mills in Mellin
space. We focus in the stress tensor four-point correlator to order $1/N^4$ and
in a strong coupling expansion. This can be regarded as the genus-one
four-point graviton amplitude of type IIB string theory on $AdS_5 \times S^5$
in a low energy expansion. Both the loop supergravity result as well as the
tower of stringy corrections have a remarkable simple structure in Mellin
space, making manifest important properties such as the correct flat space
limit and the structure of UV divergences.
