Bratislava on 12/24

By the afternoon and evening most sites will be closed. I expect few restaurants and wine bars will be open.

Any Rick Steven guide covering Vienna will include Bratislava and will have that info. So will other guide books. Given the date though, I'd use the sights's websites to double check.

Bratislava is just 39 miles from Vienna, but it's a world apart. It's a very high income, high tech and modern city. Most of the sights can be reached by foot from the docks. The Bratislava Castle is the biggest tourist sight and it should be open 9:00-5:00.
The riverfront has a very large and nice shopping mall with a bunch of restaurants overlooking the river--a very active place for sidewalk cafes when weather's nice.

Thanks, everyone. Much appreciated.