Hymettus, also Hymettos is a mountain range in the Athens area, East Central Greece. It is also colloquially known as Trellós or Trellóvouno (crazy mountain), a name of uncertain origin. In antiquity there was a sanctuary to Zeus Ombrios (Zeus the Rain God) on the summit with numerous offerings dating especially to the 8th-7th centuries BC; they are on the site of a military base and not currently accessibe. There is also an ancient quarryman's hut on the western slopes of the mountain, one of two buildings in ancient Attika which preserves its roof.
The height is 1,026 m at Evzonas and the length is 16 km (9.9 mi) between Athens and the Saronic Gulf and 6 to 7 km from east to west. In the ancient times, the highest point was known as Mega Ymittos and the southern Elattona and Anydro Ymitto (today Mavrovouni and Kontra). It was noted for its thyme honey. Marble has been quarried since antiquity. The neighboring communities that surround the mountain are Athens, Zografou, Kaisariani, Vyronas, Ilissia (a region of Zografou), Ymittos, Helioupolis, Argyroupoli, Elliniko, Glyfada, Voula and Vouliagmeni in the west, Varkiza, Vári, Markopoulo and Paeania to its east, and Papagou, Holargos, Aghia Paraskevi, Gerakas and Glyka Nera. Most of the forest is in the north, and much of the mountain is rocky, deforested, grassy and made out of limestone.