An employee works on the presentation of a sculpture by Chinese artist Ai Weiwei prior to the opening of his retrospective at the Lisson Gallery in London, May 11, 2011. The exhibition presenting a selection of the artist's works from the past six years, opens to the public May 13 and runs to July 16. Ai Weiwei was detained by authorities in Beijing, China on April 3, 2011 while trying to board a flight to Hong Kong. His whereabouts remain unknown.

Visitors walk around Ai Weiwei's "Circle of Animals/Zodiac Heads" at Somerset House in London May 11, 2011. The exhibition which comprises of 12 bronze animal heads recreated from traditional Zodiac sculptures, is on view from May 12 to June 26.