This page contains information regarding Star Trek: Short Treks, and thus may contain spoilers.
The Mona Lisa was a painting done by the Human artist Leonardo da Vinci at the beginning of the 16th century in Europe on Earth. One of the most famous works of art in Earth history, the subject's enigmatic smile has engaged viewers for centuries, and in the 20th and 21st centuries, the painting was on display at the Louvre Museum in Paris, France.
By the 24th century, Kivas Fajo was in possession of the Mona Lisa, and it was one of the centerpieces of his illegal collection. During his captivity, Data tried to mimic the Mona Lisa's famous smile. After the commander's return to the USS Enterprise-D, Fajo's collection was confiscated and the Mona Lisa returned. (TNG: "The Most Toys")