At the time of the Renaissance the Abbey fell in commendam, that is to say it was no longer the property of the community but that of the abbot, who was thenceforth chosen by the king, instead of being elected by the monks. The first commendatory abbot was the Cardinal Hippolyte d'Este, son of Lucretia Borgia. Reducing the monks to a bare pittance, the Cardinal made free use of the Abbey revenues, which enabled him to build his famous Villa d'Este at Tivoli and its magnificent gardens. In 1570, the great Italian poet Tasso spent several months at Châalis and there worked at his _Jerusalem Delivered_. [Illustration: RUINS OF THE ABBEY CHURCH] In the eighteenth century, the reconstruction of the Abbey was undertaken. Jean Aubert, the architect of the "Grandes Écuries" at Chantilly and the Hôtel Biron in Paris, was entrusted with the plans. The work was begun but not completed. The abbatial building, which to-day contains the museum and which can be seen on the left of the beautiful avenue leading to the entrance gate, shows the dignified style that Aubert wished to apply to the new edifice. All these works ran the abbey into debt so Louis XVI. had it closed and placed in liquidation. The Revolution completed its ruin. Sold as national property, Châalis greatly suffered. The buildings were for the greater part destroyed, the old church was sold piecemeal at the rate of twelve sous (6_d._) per cartful of stones. In the nineteenth century the successive proprietors did their utmost to reconstitute the domain. The grounds were bought back and the ruins consolidated. The abbatial building became a castle, and the park was laid out again. In 1902, Mme. Jacquemart-André bought the estate for 1,200,000 francs. She bequeathed it to the "Institut de France" with the museum that she had established in the castle. The "Institut" took possession of it in 1912, at the donor's death. +The Church.+ The church, built at the beginning of the eighteenth century, is of great interest from an archæological point of view, for it shows the first application (by the Cistercians) of the Gothic style of architecture which had just made its appearance in the "Ile de France." In the hundreds of abbeys created by the original abbey of Cîteaux (situated near Dijon), the Roman style had hitherto held sway. Beginning with Châalis, the Cistercians proceeded to spread the pointed arch all over Europe, where soon more than 1,800 branch abbeys were scattered. The church of Châalis was vast, measuring 269 feet by 89 feet.