Carolina Rediviva is the main building of the Uppsala University Library and the largest research library in Sweden, holding over five million volumes. The neoclassical block at the foot of Castle Hill, completed in 1841, was designed by Carl Fredrik Sundvall — a sober counterpart to the playful pink castle directly above it.
The public-facing reason to visit is the small exhibition hall on the ground floor, where the library's treasures are rotated through display cases. The permanent star is the Codex Argenteus, the sixth-century Gothic Silver Bible, alongside a Carta Marina map of the Nordic countries from 1539 and original Mozart manuscripts. The treasures room is open during library hours and free to enter.
Even if the exhibition is closed, the building is worth approaching for the views: from the terrace in front of Carolina, you get one of the best vantage points on the cathedral spires across the river.