Perhaps the world's most beautiful secular temple.
In my eyes the State Hall in Vienna's National Library, the Belvedere and Karlskirche are the perfect trio to demonstrate baroque beauty and perfection. Only 15 years separate their completion yet each one is a unique and unparalleled jewel. I suggest seeing all three to appreciate what this bombastic epoch is all about.
You don't need more than a half hour to visit the State Hall, unless the temporary exhibition attracts your attention. One display that had me glued to the glass case for ages was the very rare showing of the original score of Mozart's hand written Requiem – the one he was actually still working on when he died, quill in hand. Worthy of mention are other collections belonging to the National Library but on show in other premises: Globe Museum, Papyrus Museum and Esperanto Museum (Department of Planned Languages). The latter is home to the world's biggest technical library on inter-linguistics.