A previously unknown foot sketch by Michelangelo has sold for $23m (£16.9) - more than 10 times its original estimate.

Experts at Christie'ssay it is a foot sketch of the Libyan Sibyl, which was later painted on the Sistine Chapel ceiling.

According to the auction house, the unsuspecting owner had submitted a photograph for an auction estimate only to discover the sketch's true value.

Andrew Fletcher, global head of Christie's Old Masters Department, described the discovery as "one of the most memorable moments" of his career.

The small red chalk sketch is thought to date to about 1511-1512 when Michelangelo was preparing to work on the second half of his painting of the Sistine ceiling, which included the Libyan Sibyl.

The anonymous owner, who is based on the US West Coast, told Christie's he had inherited the drawing from his grandmother.

The man said it had been passed down through the family in Europe since the late 1700s.

A specialist in Christie's Old Master Drawings Department, Giada Damen, used infrared reflectography, which revealed drawings on the back of the sheet which also resembled Michelangelo's work.

Damen then took the foot and set it next to the Michelangelo drawing at the Metropolitan Museum, concluding the sketch was an original.

Famous pieces of art selling for millions is not unusual:

• One of the most expensive sales was in 2017 when a 500-year-old painting of Christ believed to have been painted by Leonardo da Vinci sold in New York for a record $450m

• In November 2025, a portrait of Elisabeth Lederer by the Austrian artist Gustav Klimt was sold for $236.4m in New York

• Also in November 2025, a surrealist painting by famed Mexican artist Frida Kahlo was sold for $54.7m, shattering the auction record for an artwork by a woman.