The pilgrim church "Visitation" was built between 1715 and 1803 according to plans drawn up by Prince Paul I. Esterházy. Unfortunately, the prince did not live to see the groundbreaking ceremony as he died from the plague in 1713.
The portion of the church that can be visited today represents merely the presbytery of the church originally planned. It was to be a place of worship of enormous proportions. The high altar picture "The Visitation" is a copy of a painting by Dorffmeister and dates back to 1797.
http://www.eisenstadt-tourismus.at/church-of-joseph-haydn.html