When we think of outdoor sculptures, towering statues and bold installations often come to mind. But some of the most intriguing works of public art are those that are invisible or nearly invisible, challenging our perception of space and creativity.

One notable example is *The Invisible Sculpture* by Italian artist Salvatore Garau. In 2021, he "exhibited" an invisible sculpture in Piazza della Scala, Milan, claiming it existed as a conceptual piece. Visitors were encouraged to imagine its form, proving art transcends physicality.

Another fascinating work is *The Empty Room* by Danish artist Jeppe Hein. Installed in various locations, this "sculpture" consists of an entirely empty space framed by a doorway, inviting viewers to reflect on absence and presence.

James Turrell’s *Skyspaces* are another example—architectural structures with open ceilings that frame the sky, making the ever-changing atmosphere the artwork itself. Though the structures are visible, the "sculpture" is the intangible sky.

Lastly, *The Hidden Sculpture* by Rachel Whiteread consists of negative-space casts of everyday objects, rendering them almost invisible until closely examined.

These works redefine sculpture, proving that art isn’t always about what we see—but what we feel and imagine.