  We provide a setup by which one can recover the geometry of spacetime from
local measurements of quantum particle detectors coupled to a quantum field.
Concretely, we show how one can recover the field's correlation function from
measurements on the detectors. Then, we are able to recover the invariant
spacetime interval from the measurement outcomes, and hence reconstruct a
notion of spacetime metric. This suggest that quantum particle detectors are
the experimentally accessible devices that could replace the classical 'rulers'
and 'clocks' of general relativity.
