Greenwich Meridian Laser, London - This laser points exactly north from Greenwich Royal Observatory along the prime meridian line (0 degrees longitude)
The O2 on Twitter: "Great pic“@MPSinthesky:@TheO2 with Greenwich Meridian identified by laser from Greenwich Observatory @ROGAstronomers http://t.co/udgv0WwN5v”" / Twitter
One I took - Canary Wharf from Royal Observatory in Greenwich, London with GMT laser line in shot. | Canary wharf, New york skyline, Observatory