In a beautiful canal house in Franeker/Netherland is the oldest functioning planetarium in the world. This model of the planetary system was built between 1774 and 1781 by the hobby astronomer Eise Eisinga. The “face” of the model looks down from the ceiling of what used to be his living room, with most of the mechanical works in the space above the ceiling. The planets move around the model in real time, automatically. Until today the current positions of the planets can be read. A slight “re-setting” must be done by hand every four years to compensate for the February 29th of a leap year. All this is set in motion by an impressive train of wooden tires and discs with 10,000 hand-forged nails. A pendulum clock and nine weights control this gear. The planetarium includes a display for the current time and date. The plank that has the year numbers written on it has to be replaced every 22 years.