Simplify the following text for a Grade 9 native English-speaking person.
Original: In 2003 , he initiated and conducted at the Mariinsky Theatre the first complete cycle of Wagner 's The Ring of the Nibelung to be performed in Russia for over 90 years .
Simplified: In 2003 , he conducted at the Mariinsky Theatre the first complete cycle of Wagner 's The Ring of the Nibelung to be performed in Russia for over 90 years .