Vienna, Austria...to do?

I’ve got a trip upcoming to Vienna for 10 days April 10-21. Anyone have suggestions on things to do, see, eat? Aside from a half marathon race and opera tickets I have nothing planned. Hotel booked but also open to day trip suggestions as well.

Thanks

R

Bump.

Salzburg is close by train (I think). Worth a day trip over there to explore old WW2 stuff like Hitlers Eagles Nest. Pretty incredible scenery, too.

There’s a small island off Vienna, I forget the name, but it’s covered in brightly colored houses - bright oranges, neon pinks, etc. They run tours there. The story is that the women would paint their houses bright colors so that their husbands could find them again after a long time spent at sea.