Tilda Swinton is sleeping in a glass box in a new exhibition.

The 'Moonrise Kingdom' actress surprised visitors at the Museum of Modern Art (MoMA) in New York City with her impromptu art installation, which is a revival of her 1995 performance art show, 'The Maybe'.

Tilda, 52, was seen sleeping in a transparent glass box, which was modestly equipped with a mattress, plain white bed sheets and a jug of water.

The bizarre performance art show wasn't announced beforehand and fans were shocked to see the actress on display at the museum.

Tilda will perform 'The Maybe' several times throughout the year at MoMA, however, like the first performance, they will occur at random times without a prior announcement.

A statement from MoMA read: ''An integral part of The Maybe's incarnation at MoMA in 2013 is that there is no published schedule for its appearance, no artist's statement released, no museum statement beyond this brief context, no public profile or image issued.

''Those who find it chance upon it for themselves, live and in real -- shared -- time: now we see it, now we don't.''

The quirky showcase was first performed by Tilda at the Serpentine Gallery in London in 1995 and a year later in Rome, Italy.

Stars including actor James Franco and R.E.M. singer Michael Stipe have thus far visited the actress' exhibition.