Horologion of Andronikos Kyrrhestes, Athens

The Horologion (Horologeion) of Andronikos Kyrrhestes or Tower of the Winds is anm octagonal structure built of Pentelic marble in the Roman Agora of Athens. It functioned as a sundial, water clock, and wind observer. Varro:  Inside, under the dome of the rotunda, the morning-star by day and the evening-star at night circle around near the lower part of the hemisphere, and move in such a manner as to show what the hour is. In the middle of the same hemisphere, running around the axis, is a compass of the eight winds, as in the horologium at Athens, which was built by the Cyrrestrian;  and there a pointer, projecting from the axis, runs about the compass in such a way that it touches the wind which is blowing, so that you can tell on the inside which it is ¹.

See:

1. Varro, De re rustica, Loeb Classical Library, 1934, III, 5, 17.
2. Vitruvius: De architectura libri decem I, 6

References

1. ↑Varro, De re rustica III, 5, 17.