Concerts in Vienna

Absolutely , The Musikverein ( home of The Vienna Phiharmonic ) . This spectacular hall served as the model for Charles McKim's Boston Symphony Hall ( which is why it is also terrific ) . When will you be in Vienna , and what are your tastes in music ?

By far, the most famous is the Golden Hall of the Musikverein.

The Vienna State Opera is just fabulous, if you are remotely interested in opera.

https://www.wiener-staatsoper.at/en/

These are the most renowned venues for classical concerts:
https://www.musikverein.at/en
https://www.konzerthaus.at/calendar

You may consult Austria's most comprehensive event directory: https://www.events.at/
It is in German only, but you can easily filter by location (i.e. Wien), date and type (e.g. Musik/Klassik).

If you want to book tickets online, best is to use the website of the respective venue (and not a ticket office).

Another vote for the Großer Saal at the Musikverein. One of the best places on the planet to see a concert