Rundetaarn time capsule will carry messages from people in Denmark to readers in 2126, as Copenhagen’s Round Tower prepares to reinstall its restored copper dome and begin a new phase for its historic public observatory.
The capsule will be placed in the hollow base of the tower’s century-old telescope, beneath the observatory at the top of Rundetaarn. It is designed to remain sealed for 100 years, with an inscription stating that it must not be opened before 2126.
The initiative is part of a wider restoration of the Folkeobservatorium, the public observatory that crowns one of Copenhagen’s best-known landmarks. The copper dome is due to return to the tower on 21 May, the same date on which the current observatory dome was installed in 1929.
A restored copper dome returns to Copenhagen’s skyline
Rundetaarn has been undergoing a major restoration after damage was found in the wooden structure and the copper cladding of the observatory dome. The dome was removed earlier in the year and restored at street level, allowing residents and visitors to follow conservation work that would normally take place out of sight.
According to Rundetaarn, the 2026 works are intended to preserve the observatory for future generations. The project includes the restoration of the dome, repairs to the interior space beneath it, new flooring and work on the old refractor telescope, which has been sent to specialists in Germany.
The dome’s return marks the final visible phase of the project, although the telescope itself is expected to be reinstalled later in the summer. The observatory is scheduled to reopen to the public in autumn, when darker evenings again make it possible to observe stars and planets from the top of the tower.
The Rundetaarn time capsule will hold 100 messages for the future
The Rundetaarn time capsule has been specially designed for the project and will contain selected objects from 2026 together with greetings from people in Denmark. Messages could be submitted digitally through Rundetaarn or written by hand during the public event marking the dome’s return.
Rundetaarn plans to select 100 messages that capture everyday life in 2026 and the role of the tower in Copenhagen. Christina Toldbo, head of Rundetaarn’s Observatory, told DR that the idea emerged from a simple absence: when the dome and telescope were taken down for restoration, staff wished someone from a century earlier had left a message for them.
The new capsule is intended to do exactly that for the next century. It will be sealed and placed inside the telescope’s base, where visitors will continue to look at the sky without being able to read the messages hidden beneath it.
For Toldbo, the value of the project is not only archival. She said the messages could give future Danes “a feeling of being here in 2026”, at a time when digital information will likely still be searchable but personal voices may carry a different kind of meaning.
From royal observatory to public cultural landmark
Rundetaarn was built in the 17th century under King Christian IV, who wanted an observatory where astronomers from the University of Copenhagen could study the sky above the city. Completed in 1642, the tower became part of the Trinitatis complex, together with Trinitatis Church and the former university library.
Today, however, Rundetaarn is no longer only a scientific or academic site. It is a public observatory, a viewing tower, an exhibition space and one of Copenhagen’s most recognisable cultural landmarks.
That change is central to the time capsule project. Jeanette Bursche, director of Rundetaarn, told DR that the observatory was once reserved for the university, while today it is “precisely for the people”. The invitation to send greetings to 2126 turns that public role into a physical object inside the tower.
A Nordic heritage project built around time, craft and memory
The project links three different forms of time. There is the astronomical time of the observatory, built to watch planets and stars. There is the historical time of a building that has stood in central Copenhagen since 1642. And there is the human time of handwritten and digital messages addressed to people who will live a century from now.
In that sense, the Copenhagen time capsule is more than a symbolic addition to a restoration. It gives the conservation project a civic dimension, asking people in Denmark to imagine how ordinary life, public institutions and cultural memory might look from the perspective of 2126.
For Nordic cities, where historic buildings often remain part of daily urban life, Rundetaarn’s restoration also shows how heritage can be maintained without treating it as static. The tower’s copper dome is returning to the skyline, but the message beneath the telescope is new: cultural landmarks are not only inherited from the past. They can also become a way of speaking to the future.
