The Ring of the Nibelung or, in the original German, Der Ring des Nibelungen, is a series of four epic operas. Both the libretto and the music were written by Richard Wagner over the course of twenty-six years, from 1848 to 1874.
It apparently takes four nights to perform and the theater that the poster referred to is the orignal theater that was built by the writer. It is located in Bayreuth, Germany.
According to this account there is a waiting list of several years to get tickets to that theater.
I'm impressed. Very impressed.
I am too as I have "The Ring of the Nibelungen" on cd and listen to it often but had no idea that is where that came from.