The Biblioteca Nacional de Chile is a handsome early 20th-century landmark on the Alameda, beside Cerro Santa Lucía and the Lastarria edge of the centre. It is still a working national library, so the atmosphere is more civic than touristy: reading rooms, archives, maps, newspapers, and occasional exhibitions rather than a packaged museum route.
Even if you do not need the collections, the building is worth stepping into while walking this part of Santiago. Its scale and sober neoclassical rooms say a lot about the city Chile wanted to project during its republican boom years.