Which Milan library holds Leonardo da Vinci's Codex Atlanticus?

The Milan library that holds Leonardo da Vinci’s Codex Atlanticus is the Biblioteca Ambrosiana.

The Codex Atlanticus is the largest single collection of Leonardo’s surviving drawings and writings. It contains 1,119 paper leaves arranged in 12 volumes, covering subjects such as anatomy, mathematics, astronomy, architecture, mechanics, hydraulics and flight. The pages were produced across much of Leonardo’s career, from 1478 to 1519.

The collection was assembled in the late 16th century by the sculptor Pompeo Leoni, who reorganized pages from Leonardo’s notebooks. It was acquired for the Biblioteca Ambrosiana in 1637. Napoleon’s forces later took the codex to Paris, but it was returned to Milan after the Napoleonic period.

The name “Atlanticus” refers to the large atlas-sized paper used to mount the pages, not to the Atlantic Ocean or a subject Leonardo studied. The codex is conserved and displayed at the Biblioteca Ambrosiana, often through rotating exhibitions that protect the fragile originals.