His landscapes often transitioned into the more prestigious genre of history paintings by addition of a few small figures, typically representing a scene from the Bible or classical mythology.

The earliest biographies of Claude are in Joachim von Sandrart's Teutsche Academie (1675) and Filippo Baldinucci's Notizie de' professori del disegno da Cimabue in qua (1682–1728).

According to Baldinucci, Claude's parents both died when he was twelve years old, and he then lived at Freiburg with an elder brother (Jean Gellée).

Claude then travelled to Italy, first working for Goffredo Wals [fr] in Naples, then joining the workshop of Agostino Tassi in Rome.

[9] While the details of Claude's pre-1620s life remain unclear, most modern scholars agree that he was apprenticed to Wals around 1620–1622, and to Tassi from circa 1622/23 to 1625.

He returned to Rome and settled in a house in the Via Margutta, near the Spanish Steps and Trinita dei Monti, remaining in that neighbourhood for the rest of his life.

[10] On his travels, Claude briefly stayed in Marseille, Genoa, and Venice, and had the opportunity to study nature in France, Italy, and Bavaria.

Sandrart met Claude in the late 1620s and reported that by then the artist had a habit of sketching outdoors, particularly at dawn and at dusk, making oil studies on the spot.

The first dated painting by Claude, Landscape with Cattle and Peasants (Philadelphia Museum of Art) from 1629,[11] already shows well-developed style and technique.

Baldinucci reported that a particularly important commission came from Cardinal Bentivoglio, who was impressed by the two landscapes Claude painted for him, and recommended the artist to Pope Urban VIII.

[18] Following the integration of this tradition with other Northern sources, Bolognese artists such as Domenichino, who was in Rome from 1602, painted a number of "Landscape with..." subjects, drawn from mythology, religion and literature, as well as genre scenes.

[25] The rider in the small Landscape with an Imaginary View of Tivoli in the Courtauld Gallery in London, LV 67 and dated 1642, is one of the last of his figures to wear contemporary dress.

With the mid-20th fashion for medical diagnosis through art, it was suggested that Claude had developed an optical condition accounting for such effects, but this has been rejected by doctors and critics alike.

Claude only rarely painted topographical scenes showing the Renaissance and Baroque Roman architecture still being created in his lifetime, but often borrowed from it to work up imaginary buildings.

Most of the buildings near the foreground of his paintings are grand imagined temples and palaces in a generally classical style, but without the attempt at archaeological rigour seen in Poussin's equivalents.

This view takes up the left-hand side of the painting, but on the right, behind a group of genre figures in modern dress (uniquely for Claude, these represent a scene of prostitution in the Dutch Merry Company tradition), is a statue of Apollo and a Roman temple portico, both of which are either wholly imaginary or at least not placed in their actual locations.

[31] It is pointless to question how Ascanius finds in Latium a large stone temple in a fully developed Corinthian order, that has evidently been crumbling into ruins for several centuries.

Whether the subject, and the dress of the figures, is supposed to be contemporary, mythogical or from Roman or medieval history, the large ships are usually the same up-to-date merchant vessels.

[34] In Rome, Bril, Girolamo Muziano and Federico Zuccaro and later Elsheimer, Annibale Carracci and Domenichino made landscape vistas pre-eminent in some of their drawings and paintings (as well as Da Vinci in his private drawings [1] or Baldassarre Peruzzi in his decorative frescoes of vedute); but it might be argued that not until Claude's generation, did landscape completely reflect an aesthetic viewpoint which was seen as completely autonomous in its moral purpose within the cultural world of Rome.

Perhaps to feed the public need for paintings with noble themes, his pictures include demigods, heroes and saints, even though his abundant drawings and sketchbooks prove that he was more interested in scenography.

William Gilpin, the inventor of the picturesque ideal, advocated the use of a Claude glass saying, "they give the object of nature a soft, mellow tinge like the colouring of that Master."

Hugh Sykes Davies observed their facing away from the object they wished to paint, commenting, "It is very typical of their attitude to Nature that such a position should be desirable.