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Classical Archaeology Science

A 2,000-year-old Weather Station

Most archaeological sites in Athens are ruins of temples, commercial, or public buildings. But the strange, ancient structure that stands in Athens’ Roman Agora, had a scientific purpose. Today, let’s talk about the exceptional and unique Tower of the Winds.

When it was constructed at the end of the 2nd century BCE, it included sundials, a weather vane, and even a water clock. We can presume that this 8-sided tower was effectively the first known meteorological station in the world.

Tower of the Winds (Athens, Roman Agora, ca. 50 BCE)

A marvel of science and engineering

The Tower of the Winds was a concept conceived and created by a brilliant scientist and astronomer, Andronicus of Cyrrhus. The tower was made almost entirely out of white marble, quarried from Penteli mountain. The same type of marble was used to create the Parthenon. The use of Pentelic marble is rare to find in any structures other than temples.

Built to measure time, the tower is also known as horologion, meaning timepiece. The interior of the structure contained a complicated internal metal mechanism. That metal mechanism called clepsydra, was technically a water clock. The clepsydra was driven by water flowing down from a subterranean spring under the Acropolis. This mechanism was essential for use on cloudy days or at night when the sundials of the tower were ineffective. The spring, situated on the north slope of the Acropolis, remained unknown for centuries, up until a few years ago when archaeologists located and excavated the ancient spring. To everyone’s surprise, water still flows from the same spot!

Plan of ‘Horologion’

Indicating the cardinal directions (N-S-E-W)

On the top part of the Tower of the Winds, beneath the friezes, are eight vertical sundials where the shadow was cast on hour lines. Those lines, while faint, are still visible today. The building was originally topped with a bronze weather vane depicting Triton his hand pointing in the direction from which the wind was blowing. Triton was god of the seas and oceans -as were his parents: Poseidon and Amphitrite.

Triton was placed on top so it would rotate with the wind. As the wind was blowing, the pointing rod would be positioned directly over the sculpted god, identifying the direction of that wind.

Each of the eight sides of the Tower of the Winds faces a point on the compass.
Four sides to the cardinal points of the compass (north, south, east and west) and four sides to the primary inter-cardinal points (north-east, south-east, south-west, north-west).

Each of those sides depict each of the 8 ancient Greek wind gods, giving the tower its name. The leader of the 8 wind gods was Aeolus (the main god of the wind). Those 8 gods (called Anemoi in Greek) were:

  • Boreas (north)
  • Caicias (northeast)
  • Eurus (east)
  • Apeliotes (southeast)
  • Notus (south)
  • Lips (southwest)
  • Zephyrus (west)
  • Skeiron (northwest)
Three out of the eight winds (drawing by Stewart and Revett)

Fun fact: It is from this model of the Tower of the Winds in Athens, that the custom of placing weather vanes on steeples as wind indicators, is derived (at least in the West).

Architectural influence

The ‘Tower of the Winds’ was constructed in such a stylish and elegant manner, that it inspired many Western architects over the centuries. Buildings that are based on the design of the Tower can be found scattered all over Europe -especially in England. My personal favorite example of a building inspired by the Tower of the Winds, stands in Oxford. It really is worth visiting the old Oxford Radcliffe Observatory building. The prominent octagonal tower on top of the Observatory is a wonderful scaled up version of the original tower in Athens.

Old Radcliffe Observatory building, Oxford.