The VLTI has a laboratory underground, surrounded above ground by the telescopes of Paranal. Each telescope can collect light and send it to the lab, where - after some careful control - the various light beams are recombined to synthesize that single, large telescope.
Installation of new instruments for the VLTI requires a lot of time downstairs in the lab. For my job at ESO, I'm helping to develop the PRIMA (Phase-Referenced Imaging & Microarcsecond Astrometry) instrument for the VLTI.
"Interferometry" is, even to veteran astronomers, a strange, fascinating - and sometimes scary - concept. I'll try to gently take my readers on a tour through this peculiar landscape, highlighting the important ideas and interesting results.