Yaroslavl officially celebrated it’s Millennium over the weekend of September 10th-12th, 2010.
Over the previous 2-3 years leading up to 2010, much of Yaroslavl got a face-lift. Many billions or Rubles were spent restoring many old and run-down buildings to pristine condition, old tramlines were torn up and replaced by roadways for buses and many roads were upgraded, etc.
Near the Strelka, where the Volga and the Kotorosl rivers meet, a new Cathedral of the Assumption of Our Lady was built to replace the original historic cathedral of that was built in 1659 (and destroyed in 1937).
You can read what things were like 100 days prior to the Millennium here.
After the major facelift that it has undergone. now would seem the ideal time to pay a visit to Yaroslavl.
You can see some of the preparation work for the Millennium here.
You can see an official promotional video of Yaroslavl here.