Ten years after the plan of the Large-scale Cryogenic Gravitational wave Telescope (LCGT) project, its construction started in June, 2010. The scientific objective of the project is to detect gravitational waves that are produced by astrophysical events in the Universe. Since the events are so rare that the detection capability of the detector should be enhanced to the extent where its sensitivity is limited not by technical reasons but by ultimate physics of instrument such as thermal noise, quantum noise, and so on. LCGT adopts cryogenic mirror to reduce thermal noise, which is meaningful only after ultimate sensitivity is technically attained. Cryogenic mirror is still adventurous technique after ten years of development. I present here the overview of LCGT project.