It’s the building itself that garners the most attention, a sprawling campus rebuilt in 1653 by Cardinal de Richelieu to the designs of architect Jacques Lemercier. A blend of Baroque and Renaissance styles replaced the original medieval structure, but the last remaining building from this period is the iconic domed Romanesque Chapelle de la Sorbonne (the Chapel of La Sorbonne), where the sculpted tomb of Cardinal de Richelieu is housed. A wander through the Sorbonne courtyard and café-lined plaza offers views of the amphitheaters, library and observatory (which was reconstructed by Henri Paul Nénot in the late 19th-century), showcasing a picturesque variety of architectural styles.
Today, the building houses four divisions of the prestigious University of Paris -- the Pantheon-Sorbonne University, the Sorbonne Nouvelle University, the Paris-Sorbonne University and the Paris Descartes University -- as well as the extensive Sorbonne Library, and is open to the public only through pre-book guided tours.
We enjoyed our hop on hop off tour, we took the 2 day option which gave us plenty of time to see all of the sights or allow us time to plan visits to museums etc. Our hotel was close to the Sorbonne so it was easy to find the correct bus and the right stop.