The Primatial Basilica of the Blessed Virgin Mary taken into heaven and St. Adalbert is an ecclesiastic basilica in Esztergom, Hungary, the mother church of the Archdiocese of Esztergom-Budapest, and the seat of the Catholic Church in Hungary.
It is dedicated to Saint Mary the Assumption and Saint Adalbert.

Anyway, it is the largest church in Hungary and the 3rd largest in Europe.

Esztergom:
is a city in northern Hungary, 50 km north-west of Budapest.
It lies on the right bank of the river Danube, which forms the border with Slovakia there.
Esztergom was the capital of Hungary from the 10th till the mid-13th century
and was the Royal Seat until King Béla IV of Hungary moved to Visegrád and later to Buda.
Esztergom still is the seat of the Primate of the Roman Catholic Church in Hungary.