Gotterdammerung, the final night of Richard Wagner's music drama Der Ring des Nibelungen had it premiere on August 17, 1876 at the Bayreuth Festspielhaus. You can get more info from the Wikipedia entry on the history of the work and it's significance by clicking on the image above.
For me the work is a huge, epic rollercoaster ride of emotion. More than almost anywhere else in the cycle are the emotions behind the music so close to the surface, from the sense of total ecstasy in the love duet of the prelude, the betrayal of Act 1 and the desolation of Act 2 to the sense of spiritual cleansing and renewal in the conclusion. In performance it has a huge impact on me and I rarely emerge from the experience dry eyed.
The footage below is a behind the scenes look at the making of the great Georg Solti Ring for Decca, produced by John Culshaw. These are the final moments of the Immolation Scene filmed by the BBC with Birgit Nilsson as Brunnhilde. Quite possibly the greatest recording achievement to date.