  We calculate bulk and boundary correlators in JT gravity by summing over
geometries. The answers are reproduced by computing suitable ensemble averages
of correlators of chaotic quantum systems. We then consider bulk correlators at
large spatial separations and find that semiclassical decay eventually makes
way for erratic oscillations around some nonzero answer. There is no cluster
decomposition because of wormholes connecting distant regions. We construct
more microscopic versions of JT gravity which are dual to a single quantum
system by including a set of branes in the gravitational theory the data of
which describes the Hamiltonian of the dual system. We focus on the bulk
description of eigenstates which involves end of the world branes and we
explain how observables factorize due to geometries connecting to these branes.
