PENTELICUS (Βριλησσός, or Πεντελικὸν ὄρος from the deme Πεντέλη; mod. Mendeli), a mountain to the N.E. of the Athenian plain, height 3640 ft. Its quarries of white marble were not regularly worked until after the Persian wars; of this material all the chief buildings of Athens were constructed, as well as the sculpture with which they were ornamented. The ancient quarries are mostly on the south side of the mountain. The best modern quarries are on the north side. The top of Pentelicus commands a view over the plain of Marathon, and from it the Athenian traitors gave the signal to the Persians by a flashing shield on the day of the battle. There was a statue of Athena on the mountain.