The smoke of the fire in East Attica covered the sun.
UPDATE: maybe I did not explain well enough... That orange sky may be very beautiful, like a Terner's painting -that is what I also thought at first, but it is because of the big fire in East Attica which keeps on for 3rd day today, burning the suburbs and taking people out of their homes.
The Monetary Museum is in Panepistimiou str a few metres form Syntagma metro station. A beautiful old building designed by architect Ernst Ziller, that used to be Heinrich Schliemann'shome, named Iliou Melathron (=palace of Ilion).
This is the view while entering the garden
and this is the way Panepistimiou str is (not!) seen from the garden.
There is a cute, quiet coffee shop in the garden behind the building, where you can have some time of peace and rest, away from the noise and the sun!