While the Light Hesitates

Uniquely in 2026, our visitors can experience a spectacular light installation atop the Round Tower. “While the Light Hesitates”, created by the design studio Yoke, launches the program Light Year 2026 and invites both tower visitors and passers-by to sense the nature of light through scale, space and time.

A central element of astronomer Ole Rømer’s discovery of the speed of light – which the Round Tower marks the 350th anniversary of this year – is his observation of Jupiter’s innermost moon, Io. Drawing on Rømer’s observations of Io, the work unfolds the nature of light in three acts through scale, space and time. As darkness falls, the hesitation of light is transformed into circular light formations that recall the moment when light reveals its speed. The immersive experience is supported by a soundscape.

“While the Light Hesitates” is activated after dark and can be experienced atop the tower and from the surrounding city for a limited time period – an exceptional opportunity to see the Round Tower’s iconic platform with new eyes. Normally, as little light as possible is used at the top of the tower, as it would disturb the view from the Observatory; however, as the Observatory is being restored in 2026, this presents a rare chance to experience light art and science hand in hand nearly 35 meters above Copenhagen.

Yoke brings together technology, space and storytelling in sensory and interactive works that explore how we experience and understand the world. As storytellers, designers, creative technologists, and makers, they work at the intersection of art, design, and communication – driven by curiosity and a desire to turn knowledge into experience.

The light installation is part of the program for Light Year 2026 – a full year dedicated to celebrating light and the 350th anniversary of Ole Rømer’s groundbreaking discovery of the speed of light.

The work can also be experienced as part of the annual Copenhagen Light Festival.

Create Stunning Blue Images with Cyanotype

Experience the magic of light in this family workshop.

How can light create images in captivating shades of blue? You and your family can find out when the Round Tower, in connection with the photo exhibition Ad Lucem, invites children and adults to a creative workshop.

Together with artist Cecilia Ömalm and astronomy professor Göran Östlin—the creators of the exhibition—you’ll have the chance to make your own light prints using cyanotype, a historical photographic technique invented by astronomer John Herschel. The technique traditionally uses iron salts mixed into UV-sensitive solutions which, together with sunlight, form images in characteristic deep-blue tones.

In this workshop, we work with UV light and small glass negatives featuring space-themed motifs, which we will transform into beautiful cyanotypes.

Join us for a creative family workshop that brings together art, science, and curiosity—where you’ll learn the technique and take home your own blue masterpieces! With the same ticket, you can also explore the exhibition and the rest of the Round Tower.

Lantern Walk for Children

Join us for a special evening for families with children in the Round Tower, where we brighten the darkness and create artistic lanterns.

Have you ever experienced the Spiral Ramp in the dark? Find your way to the open workshop in the Library Hall, where you can craft your own imaginative lantern to help you find your way further up through the tower.

Afterwards, you can go exploring with your glowing lantern — and with your parents — in hand, all the way to the top of the old tower.

Please note: This event is for families with children only and is part of the programme for LIGHTYEAR 2026 at the Round Tower — a full year in which we celebrate light and the 350th anniversary of Ole Rømer’s groundbreaking discovery of the speed of light.

Workshop: Paint with Light

Join us as we play with light and long exposure times to create beautiful images together with astrophysicist and head of the Round Tower’s observatory, Christina Toldbo.

What is light? And how did the Danish astronomer Ole Rømer discover 350 years ago that light has a speed? Get the answers when the Round Tower’s observatory director, Christina Toldbo, tells more about astronomer Ole Rømer and his major discovery, which remains important to us today.

When we capture light from the Universe with our bare eyes, there’s a limit to how long we can keep them open. Luckily, we have cameras that can collect light for much longer! This is why astrophotographers can take stunning photos of faintly glowing nebulae and galaxies.

In this workshop, we’ll also use cameras to collect light and create light art with long exposure times and different light sources — including flashlights and Christmas lights! You’ll even get to print your own light-art photo and take it home with you.

Workshops will be held on both February 9 and 10 from 11:00 to 13:00.
Participation is free once admission to the Round Tower has been paid.

Planet Workshop for Kids

Let your creativity run free and create your own planets or Solar system when the Round Tower invites you to a creative drop-in workshop for children.

Create unique and imaginative celestial bodies! Armed with scissors, glue, cotton balls and crayons, only imagination sets the limits.

The Round Tower provides tools and drawing kits, but you decide the patterns and colors of your celestial creations.

The workshop is open to all who have paid regular admission, though spaces are limited.

The event is part of the program for Round Tower’s astro festival “KOSMOS”.