LIGO Hanford beam tube

LIGO's twin detectors are separated by more than 3000 km (approximately 1865 mi.). Above, guests at the Advanced LIGO Dedication held on May 19th, 2015 gaze down one of two 4-km (2.5-mi) beam tubes of the Hanford detector in eastern Washington. The small cube-shaped building appearing to sit at the 'end' of the tube is actually the arm's 'mid station', 2 km (1.25 mi.) distant. The end station, 4 km away, is not visible.