The Mona Lisa is much smaller than visitors expect

Leonardo da Vinci's Mona Lisa measures just 77 by 53 centimetres — roughly the size of a large laptop screen. Visitors to the Louvre consistently describe being surprised by how small it is, often having expected something monumental. It is displayed behind bulletproof glass, guarded by a railing, and usually surrounded by crowds photographing it from 5 metres away. The painting's fame is partly self-reinforcing: it became the most famous artwork in the world largely because it was stolen in 1911, its absence sparking global coverage. It languished in relative obscurity before the theft.

Source: Sassoon, Becoming Mona Lisa: The Making of a Global Icon (2001)