Viola collaborated with the industrial rock band Nine Inch Nails and its lead singer Trent Reznor to create a video suite for the band's tour. The triptych mainly is focused on water imagery and was supposed to be integral with the songs that were played. An Ocean Without a Shore In 2007, Viola was invited back to the 52nd Venice Biennale to present an installation called "Ocean without a Shore," which was seen by over 60,000 viewers throughout its duration. The work consists of people standing in the foreground with nothing but black behind them. Each of them seem to produce gallons of water from themselves as if they were waterfalls. The water comes gushing out of their bodies as if they are being reborn. The piece who only seem to trickle water, while all the others produce a waterfall of water (Sal 2008). Viola says that this piece is about how the dead are undead; that once they get through the water they are conscious again. Observance Observance 2002, is a work which may be taken partly as a response to the September 11, 2001 Terrorist Attacks. The Tristan Project In 2004, Viola embarked on The Tristan Project. At the invitation of opera director Peter Sellars, he created video sequences to be shown as a backdrop to the action on stage during the performance of Wagner's opera Tristan und Isolde. Using his extreme slow motion, Viola's pieces used actors to portray the metaphorical story behind Wagner's story, seeing for example the first act as an extended ritual of purification in which the characters disrobe and wash themselves before finally plunging headlong into water together (in Wagner's story, the two characters maintain the facade of being indifferent to each other (necessary because Isolde is betrothed to Tristan's uncle) before, mistakenly believing they are going to die anyway, and reveal their true feelings). The piece was first performed in Los Angeles at Disney Hall on 3 separate evenings in 2004, one act at a time, then given complete performances at the Bastille Opera in Paris in April and in November 2005. The video pieces were later shown in London without Wagner's music in June to September 2006, at the Haunch of Venison Gallery and St Olave's College, London. The Tristan project returned, both in music and video, to the Disney Hall in Los Angeles in April 2007, with further performances at