A radio-controlled flying witch makes a test flight past a moon setting into clouds along the pacific ocean in Carlsbad, California October 8, 2014. Reuters was invited to photograph the testing of the life sized device by inventor Otto Dieffenbach lll. (Photo by Mike Blake/Reuters)

A partially frozen Niagara Falls is seen on the American side lit by lights during sub freezing temperatures in Niagara Falls, Ontario March 3, 2014. (Photo by Mark Blinch/Reuters)

Beneath the Swedish capital lies an intricate web of underground train lines. More than 90 of the 100 stations in the 110km tunnel system, sometimes referred to as “the world’s longest art gallery”, have been decorated with paintings, installations, mosaics and sculptures by 150 artists since the 1950s. After spending a couple of weeks exploring arctic Norway and Sweden, London-based travel photographer Conor MacNeill headed underground to capture images of the metro stations. Here: A rainbow arcs over a girl on the platform of Stadion station. (Photo by Conor MacNeill/The Observer)

The “Strandbeest” sculpture created by Dutch artist Theo Jansen walks at Federation Square on February 1, 2012 in Melbourne, Australia. The 12 metre long, 4 metre high and 2 metre wide structure built of plastic tubes and bottles designed to walk using wind energy will be on display at Federation Square until February 26. (Photo by Scott Barbour/Getty Images)

Jo Jo performs at the Q102 s*xy Singles 2012 the at Hotel Palomar on January 26, 2012 in Philadelphia, Pennsylvania. (Photo by Gilbert Carrasquillo)