Prototype Large-Sized Telescope, named LST-1. This telescope is the first of four LSTs on the Cherenkov Telescope Array (CTA) site at the Observatorio del Roque de los Muchachos on the island of La Palma, Canary Islands. The LST has a 23-metre diameter parabolic reflective surface which collects and focuses Cherenkov light into the camera. Cherenkov light is emitted by charged particles when high-energy gamma rays from space strike the atmosphere. The telescope is designed to indirectly detect gamma rays produced billions of years ago by cosmic sources. The telescope was built in 2018. Photographed in 2019.