Being a big fan of ice skating, this is definitely the #1 winter event in Vienna for me! Every year between the end of January and the beginning of March the huge square in front of the Rathaus (City Hall) is converted into an open air ice rink where you can join fellow Viennese and skate to the sound of wiener waltzes or current disco tunes (depending on the time of day or if there are special events) from 9am to 10pm.
The Rathaus is lit very impressively, so you can't help but *feel* the pace of Vienna skating to the rhythm of a waltz and looking up at the gorgeous building illuminated with thousands of colorful lights.
You can rent a pair of skates for 6 euros. Admission is done in 5 blocks (of 2 1/2 - 3 1/2 hours of length with admission prices between 3.30-5.50 euros), but there are also day passes for 8.00 euro, and a special evening ticket that puts you on the ice from 7.30pm till 11pm for the price of 6.30 euros. Discounts for Students, seniors and children.
For more information about this event, see the official website.