Hieronymus Bosch, The Garden of Earthly Delights, 1503–1515
This fantastical triptych is generally considered a distant forerunner to Surrealism. In truth, it’s the expression of a late medieval artist who believed that God and the Devil, Heaven and Hell were real. Of the three scenes depicted, the left panel shows Christ presenting Eve to Adam, while the right one features the depredations of Hell; less clear is whether the center panel depicts Heaven. In Bosch’s perfervid vision of Hell, an enormous set of ears wielding a phallic knife attacks the damned, while a bird-beaked bug king with a chamber pot for a crown sits on its throne, devouring the doomed before promptly defecating them out again. This riot of symbolism has been largely impervious to interpretation, which may account for its widespread appeal.

Gustav Klimt, The Kiss, 1907–1908
Opulently gilded and extravagantly patterned, The Kiss, Gustav Klimt’s fin-de-siècle portrayal of intimacy, is a mix of Symbolism and Vienna Jugendstil, the Austrian variant of Art Nouveau. Klimt depicts his subjects as mythical figures made modern by luxuriant surfaces of up-to-the moment graphic motifs. The work is a highpoint of the artist’s Golden Phase between 1899 and 1910 when he often used gold leaf—a technique inspired by a 1903 trip to the Basilica di San Vitale in Ravenna, Italy, where he saw the church’s famed Byzantine mosaics.

Vincent van Gogh, The Starry Night, 1889
Vincent Van Gogh’s most popular painting, The Starry Night was created by Van Gogh at the asylum in Saint-Rémy, where he’d committed himself in 1889. Indeed, The Starry Night seems to reflect his turbulent state of mind at the time, as the night sky comes alive with swirls and orbs of frenetically applied brush marks springing from the yin and yang of his personal demons and awe of nature.

Johannes Vermeer, Girl with a Pearl Earring, 1665
Johannes Vermeer’s 1665 study of a young woman is startlingly real and startlingly modern, almost as if it were a photograph. This gets into the debate over whether or not Vermeer employed a pre-photographic device called a camera obscura to create the image. Leaving that aside, the sitter is unknown, though it’s been speculated that she might have been Vermeer's maid. He portrays her looking over her shoulder, locking her eyes with the viewer as if attempting to establish an intimate connection across the centuries. Technically speaking, Girl isn’t a portrait, but rather an example of the Dutch genre called a tronie—a headshot meant more as still life of facial features than as an attempt to capture a likeness.

Leonardo Da Vinci, Mona Lisa, 1503–19
Painted between 1503 and 1517, Da Vinci’s alluring portrait has been dogged by two questions since the day it was made: Who’s the subject and why is she smiling? A number of theories for the former have been proffered over the years: That she’s the wife of the Florentine merchant Francesco di Bartolomeo del Giocondo (ergo, the work’s alternative title, La Gioconda); that she's Leonardo’s mother, Caterina, conjured from Leonardo's boyhood memories of her; and finally, that it's a self-portrait in drag. As for that famous smile, its enigmatic quality has driven people crazy for centuries. Whatever the reason, Mona Lisa’s look of preternatural calm comports with the idealized landscape behind her, which dissolves into the distance through Leonardo’s use of atmospheric perspective.