Vienna - Underground passage

It may be the underground passage/exit from the Karlsplatz Metro station:

The other Karlsplatz Station exit is two blocks away at the intersection of Opernring, Kärntner Ring, and Kärntner Strasse, directly in front of the building of Vienna State Opera.

So you may be able to enter the Metro station below the Ringstrasse and walk to the other entrance. But you have to cross streets to get to the lower entrance. Google Maps suggests the 59A bus.

There is an underground passage from the Staatsoper to Karlsplatz. Enter it at the entrance closest to Cafe Sacher and walk all the way to Karlsplatz, opposite the Hotel Bristol. This is a way to avoid the traffic on the Ringstrasse. No, thentrances/exits are not hard to find. I don't use the maps.

This long underground passage extends from Karlsplatz to the Opera building and has 10+ entrances. There is one entrance right in the front of the Secession building.

It is no problem walking on street level. Everywhere are pedestrian crossings with traffic lights. You just have to wait until the lights are green; J-walking is discouraged.

The only time I walk through the passage is if it raining. Traffic is a non- issue - there are very civilized traffic lights here.

That said, there is an entrance to the passage at the corner of the Secession building which, if you follow the signs to Oper, take you directly to the entrance of the Opera House.

Thanks for all the helpful replies!