The world's oldest working planetarium is hidden inside a Dutch living room ceiling

Countries & Cities · Published 29 September 2026 Swipe more like this →

In short: In a quiet canal house in Franeker, an amateur astronomer spent seven years building a mechanical solar system. Completed in 1781, this intricate orrery still tracks the planets in real time. It is a masterpiece of 18th-century engineering that now holds the prestigious status of a UNESCO World Heritage Site.

Between 1774 and 1781, Eise Eisinga, a local wool carder, transformed the ceiling of his living room into a functional model of the solar system. The mechanism, which remains the oldest working orrery in the world, is driven by a pendulum clock featuring nine weights. It tracks the Sun, Moon, and six planets—Mercury, Venus, Earth, Mars, Jupiter, and Saturn—at a scale of one to one trillion. To build the complex gear system required for this precision, Eisinga hand-forged 10,000 individual nails.

The planetarium is not merely a static display; it operates automatically in real time. While remarkably exact, the system is subject to physical limitations, such as the pendulum being influenced by temperature fluctuations because it is crafted from a single type of metal. Furthermore, the model requires minor manual maintenance to remain accurate: a reset is performed every four years to account for leap years, and the wooden plank displaying the current year must be replaced every 22 years.

The site’s historical significance eventually caught the attention of royalty, leading William I, the first King of the Netherlands, to purchase the house. Today, the museum preserves not only the planetarium but also Eisinga’s former wool-combing workshop and a collection of 18th-century astronomical instruments, including octants and Georgian telescopes. Recognized as a top 100 Dutch heritage site since 1990, the planetarium was officially inscribed as a UNESCO World Heritage Site in September 2023, cementing its legacy as a triumph of amateur scientific achievement.

Beyond the basic orbital mechanics, the display includes features for tracking lunar phases and other astronomical phenomena. The zodiac is also depicted on the ceiling, which is finished in royal blue with gold accents. Visitors can view the mechanical works housed in the space above the living room, offering a rare glimpse into the ingenuity required to map the heavens from the comfort of a private home.

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