• No prams on the platform, since the ramp ends in two staircases (59 steps); park the pram by the ticket booth or before the wooden stairs
• Telescope evenings on Mondays and Tuesdays in winter, included in the ticket; on cloudy nights the astronomers talk about the dome and the telescope instead
• Tickets at the door only, card preferred, and the queue at busy times rarely tops 20 minutes

Christian IV built the Round Tower in 1642 as an observatory. Instead of stairs, a wide cobbled spiral ramp winds up past the Library Hall and its changing exhibitions, then two short staircases lead to an open platform 34.8 m above the street, with views over the old town's rooftops.

On winter evenings, astronomers open the dome and let kids look through the 1929 telescope at the Moon or planets.