Whereas at St. Peter's, the Harmoniemesse was played, another Mass, the sublime Schöpfungsmesse ("Mass of Creation" in B flat major, H. 22/13), was sung at the Mass of Pentecost at the Bergkirche in Eisenstadt, Austria, former seat of the court of the Princes Esterházy. This is the same church in which it was sung for the first time on 13 September 1801 and in which Haydn himself is buried.
The Mass was celebrated by the Bishop of Eisenstadt, H.E. Paul Iby. You can watch the entire Mass at this link (thanks to reader Scott for the tip).
There are various elements of this celebration which one might point out, both positively and critically. One thing I noticed was the rather intelligent camera direction: they had, e.g., the mindfulness of showing the tumba-shaped altar at the "sepultus est" of the Credo.
