Charles-Louis Clérisseau (28 August 1721 – 9 January 1820) was a French architect, draughtsman, antiquary, and artist who became a leading authority on ancient Roman architecture and Roman ruins in Italy and France. With his influence extending to Russia, England, and the United States, and clients including Catherine the Great and Thomas Jefferson, Clérisseau played a key role in the genesis of neoclassical architecture during the second half of the 18th century. Education; career in Rome Born in Paris, Clérisseau was a pupil of the architect Germain Boffrand. In 1746, in his mid-twenties, he won a Premier Prix de Rome in the architectural competition to design Un grand hôtel, or great mansion. The prize included a scholarship to study in Rome, and in 1749 Clérisseau became an official pensionnaire (resident) at the French Academy in Rome, where his instructors included the painter of ruins Giovanni Paolo Pannini. In Rome he also befriended Giovanni Battista Piranesi and Claude-Joseph Vernet, and in 1752 the three of them set out on a sketching tour of Hadrian's Villa at Tivoli. Before beginning to draw, the three first had to cut and burn away the undergrowth, where lurked colonies of venomous snakes and scorpions. In 1753, Clérisseau's final months at the Academy were marred by a bitter dispute with its director, Charles-Joseph Natoire. Clérisseau was for a time expelled, but was eventually allowed to return and complete his scholarship. In 1755 the Scottish architect Robert Adam arrived in Florence, where he met Clérisseau, who accompanied him to Rome; there the ambitious Adam resolved, under thea of Clérisseau, to produce a volume for publication upon his return to Britain that would establish him as a serious architect. The project finally selected was a volume documenting the ruins of Diocletian's Palace at Split, on the Dalmatian coast. Over a period of five weeks in 1757 Adam sketched and supervised the documentation of the ruins, while Clérisseau produced perspectives, and two German draftsmen undertook the measured drawings. Most of the published engravings in Adam's Ruins of the Palace of the Emperor Diocletian at Spalatro (1764) are believed to be the work of Clérisseau, though he received no credit. Clérisseau passed most of the next decades in Rome. As it had done since the High Renaissance, ancient Rome and modern Rome functioned as a cultural hub, the ruins of Classical Antiquity providing a school in themselves, if one had