Best Cathedral or church for Sunday High Mass

St. Stephens in Vienna is the place.

The other incredible duomo in my eyes is in Cologne. It was the tallest structure in the world for something like 600 years--until the Eiffel Tower was built in the 1880's.

I have gone to Sunday mass at St Stephens in Vienna and it was very impressive and so glad that I went,I have also gone to Sunday mass at Salzburg Cathedral and the choir and organ were fabulous.St Stephens is larger but either one will fill the bill.
Mike

Actually, the place to go in Vienna for excellent choral and organ music during Sunday mass is the Augustiner Kirche, which is part of the Hofburg complex. Go early to get a seat as this is one where you also find many locals.

Here in a descriptive link:

https://www.wien.info/en/sightseeing/sights/from-a-to-f/augustinian-friars

In Salzburg, Franziskanerkirche on Sunday at 9am or the Cathedral on Sunday at 10am. You can check in advance, even online, what they will be singing so you can plan. The acoustics at Franziskanerkirche is a little better but the Cathedral, being larger, has more seating opportunities. Absolutely exceptional are concerts in the Cathedral where five different organists improvise at the same time on its five organs, but of course such concerts are not frequent.

http://www.franziskanerkirche-salzburg.at
http://www.kirchen.net/dommusik/home/

FYI, Franz Schubert's Mass in G major is featured at the Augustinerkirche at 1100 on May 8.

May want to check out info about the high mass at the chapel in the Imperial Palace with members of the Vienna Boys Choir . Small cost, but I think it will be worth it.