Vrilissia is a suburban town and a municipality of the North Athens regional unit, in the Attica region. It is located in the Athens basin, at the southwestern foot of the Penteli Mountain. At the 2021 census, the municipality had 32,417 residents.

Mount Pentelicus or Pentelikon is a mountain in Attica, Greece, situated northeast of Athens and southwest of Marathon. Its highest point is the peak Pyrgari, with an elevation of 1,109 m. The mountain is covered in large part with forest, and can be seen from southern Athens (Attica), the Pedia plain, Parnitha, and the southern part of the northern suburbs of Athens. Houses surround the mountain, especially in Vrilissia, Penteli, Ekali, Dionysos, and north of Gerakas. Marble from Mount Pentelicus is of exceptionally high quality and was used to construct much of the Athenian Acropolis. Later, Pentelic marble was exported to Rome, where it was used in construction and in sculptures.