Now the sculptor and painter who divides her time between Germany and the United States returns to the city with an intriguing spatial sculpture exhibit designed for the rotunda space at the Schirn Kunsthalle.

The exhibit, called "Schrei mich nicht an, Krieger!" combines the modern, manmade forms of metal with the organic texture and flow of sand. The sand takes the visitor a bit by surprise as it drifts from an open balcony above the circular rotunda floor and sifts into the containers below.

The artist placed two aluminium sculptures that are open at the top and filled with sand, one each at the opposite entrances to the rotunda space – a space that is how the rest of the first-floor galleries and other work are accessed. It is not clear at first how this sand came to be in and on top of the objects, the Schirn explains.

The installation is supported by a system of colors that draw the visitor's eye upward and along the existing rotunda architecture, where sand trickles down and into the aluminium. As guests stroll the space, walking in and out of the galleries, they move the sand and participate in the project.

"Children have quickly realized what is going on in this installation," said critic Michael Hierholzer. "Intuitive and impulsive, they scoop the material out with their hands and feet."

That's what Lena Henke wanted, he adds. But is that all? There are complex layers and textures here too.

The shiny aluminium container with soft, waveform contours awaits in the rotunda space, covered by a coarse-meshed, metal grill through which sand passes as it falls from the passage above. Its partner also waits in the rotunda, which Henke says she is using – in her minimalist style -- to connect the creative and performative interior spaces of the gallery with the urban exterior and streetscape at the door. That mission is assisted by the paving stones on the floor, which in spots are covered in eddies of fallen sand.

Above the entire installation is an eye on the ceiling that reveals what the two aluminium sculptures also are: eyes wide open, with sand falling into them. Henke's installation then evokes the sense of irritation one feels as the sands – of time, of irritation, of opportunity or regret – keep annoying their witnesses. It is perhaps on the upper floors, with one locked barrier in the circle, that one truly sees the sculpture clearly.

As a sculptor, Henke is familiar with sand and its use in castings. Yet she also walks the shoreline in New York City, scrutinizing the castaway toys and trash that litter the sand with the tides and contemplating the powerful forces that put them there. Sand previously appears in her works, including a 2015 series called "female fatigue," and the 2014 sculpture Die.

"The smooth, cool aluminium from which Henke fashioned the eyes is another important material in her work," the Schirn said. "The sand, which absorbs the light, forms a contrast to the silver reflections of the aluminum. The artist tosses sand in our eyes: this interaction of disparate materials, qualities, and associated experiences is both disrupting and disquieting."