Lier Astronomical Clock And The Zimmer Tower

Lier is a small town in northern Belgium, known for its medieval city centre and two UNESCO sites. It is also home to a wonderful timekeeping curiosity: the Zimmer Tower and its Astronomical Clock.

Located at the top of the Zimmerplein, the tower is unmissable with its huge dial with thirteen different time metrics. The Zimmerplein is packed with bars and restaurants, ensuring the clocks have a wide audience.

The Jubilee Clock of the Zimmer tower

History of the Zimmer Tower

The tower started life as a fortification in the historic Belgian city of Lier, built around 1425 as a keep. By the end of the First World War, it was considered obsolete and marked for demolition.

The tower was saved in large part due to to astronomer and clockmaker Louis Zimmer. He had plans to restore and renovate the tower. In 1930, in honour of Belgium’s 100th anniversary of independence, he donated his masterpiece, the Jubilee Clock, to the tower. The tower, previously called the Cornelius Tower, was renamed the Zimmer Tower in his honour.

Urban sketching zimmer tower square in lier belgium
The Zimmer Tower, in the centre of Lier

Inside the Zimmer Tower

The first floor of the Zimmer Tower is the Astronomical Studio, which features a revolving planetarium that shows the northern hemisphere. On the second floor is the clock mechanism, which drives all of the clocks that make up the Jubilee clock.

The Jubilee Clock

The Jubilee Clock has twelve dials that surround a central clock that shows the local time. Some of the others clearly aren’t clocks, but they still display some pretty interesting information. So, what do they do?

Starting at the 12 o’clock position, and moving clockwise, they are:

The phases of the moon

The rotating gold and blue sphere shows the phase of the moon, telling us whether there is a new moon, crescent moon, gibbous moon or full moon. The phase lasts 29.53 days.

The metonic cycle

This cycle revolves every 19 years, at which point the moon phases fall on the same days of the year. The outer hand points to the year of the 19-year cycle, and the inner cycle shows the age of the moon for the 1st January of the current year.

The equation of time

This interesting dial is the difference between the apparent and mean solar time, measured in minutes. That is, the position of the sun as we see it, compared to a theoretical mean sun.

The signs of the zodiac

This year-long dial shows the signs of the zodiac, and the symbols that correspond with each of the stellar constellations.

The solar cycle

The solar cycle turns every 28 years, after which the dates line up in the same order again. The outer dial shows the current year of the cycle, whilst the dominical letter (denoting the day that the year’s first Sunday falls) in shown on the inside dial.

The week

This dial shows the days of the week, as well as their associated Roman god and symbol.

The globe

The globe turns every 24 hours, with the visible side showing which part of the earth is currently in daytime.

The months

The months according to the Gregorian calendar are shown here with their associated symbols.

The calendar dates

The calendar dates are accurately shown here, with a calendar month being 31 days. For months with 30 or less days, the dial skips to the next month.

The seasons

The seasons are displayed, along with artwork from local artist Felix Timmermans. Spring is represented by a child holding flowers, summer is a mower, autumn a cornucopia, and winter and old lady reading a book at the fireplace. The precise lengths of each season in days and hours is also shown.

The tides

Completing two cycles per day, these boat symbols indicate the rising and falling tides at Lier.

The age of the moon

The age of the moon is the number of days since the last new moon. The clock measures its position in the 29 day, 12 hour, 44 minute revolution between full moons. in other words, one revolution around the earth.


Lier is a wonderful day trip from Antwerp, and visitors to Belgium should certainly take the time to a make a day trip to this city. The Zimmer Tower and the interesting Jubilee clock is just one of the great sights that Lier has to offer.

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