Paranal tunnels: A peek underneath the Very Large Telescope

The Very Large Telescope (VLT) at Paranal Observatory in northern Chile is the world's biggest optical telescope.

Run by the European Southern Observatory (ESO), it became fully operational in 2000 and is packed with cutting-edge instruments.

Jean-Philippe Berger, an ESO engineer and a specialist in interferometry, took BBC News underneath the VLT to show how the technology works.

Produced by Katia Moskvitch and Susannah Reid.