  We present here a new method using interferometric measurements of quasars,
that allows the determination of direct geometrical distances on cosmic scales.
Quasar Broad Emission Line Regions sizes provide a "meter rule" with which to
measure the metric of the Universe. This method is less dependent of model
assumptions, and even of variations in the fundamental constants (other than
c). We discuss the spectral and spatial requirements on the VLTI observations
needed to carry out these measurements.
