Liupanshui, Laser Interferometry Gravitational Wave Observatory.
Currently, there are four countries in the world that have six gravitational wave observatories.
America owns two observatories in Washington State with arm lengths of 4 kilometers and 2 kilometers respectively (LHO), and Washington State has a 4-kilometer arm length observatory (LLO).
They are all part of the LIGO detection system and are, to date, the most advanced and sensitive gravitational wave detection devices. They have been constantly upgraded, with laser power now increased by twentyfold, and sensitivity ten times greater than the original version.
Then there's Italy's VIRGO (Virgo) Observatory in Pisa, with an arm length of 3 kilometers. It officially joined the LIGO network in August of last year to detect gravitational waves, and its sensitivity is on par with America's three observatories.
