With our EuroRail passes, we added a few extra days of travel so we could do day trips. We already had purchased Germany, Denmark, and Austria (and Ashton had France because she took the train to Hamburg first) so adding days of travel isn’t tooo much more expensive and was well worth it. In Sweden, we took day trips to Stockholm and Copenhagen with the train, and in Austria, we just took one to Salzburg.
New Year’s Day we designated for Museumsquartier (the museum quarter) because Vienna has so many amazing museums. Wikipedia puts it into numbers: “The Museumsquartier is a 60,000 m² large area in the 7th district of the city of Vienna, Austria; it is the eighth largest cultural area in the world.” Hence why Ashton wanted to make a day of it.