  KAGRA is a 3-km interferometric gravitational wave telescope located in the
Kamioka mine in Japan. It is the first km-class gravitational wave telescope
constructed underground to reduce seismic noise, and the first km-class
telescope to use cryogenic cooling of test masses to reduce thermal noise. The
construction of the infrastructure to house the interferometer in the tunnel,
and the initial phase operation of the interferometer with a simple 3-km
Michelson configuration have been completed. The first cryogenic operation is
expected in 2018, and the observing runs with a full interferometer are
expected in 2020s. The basic interferometer configuration and the current
status of KAGRA are described.
