Athens sprawls across the central plain of Attica that is often referred to as the Athens or Attica Basin. The basin is bounded by four large mountains: Mount Aigaleo to the west, Mount Parnitha to the north, Mount Pentelicus to the northeast and Mount Hymettus to the east. Beyond Mount Aegaleo lies the Thriasian plain, which forms an extension of the central plain to the west. The Saronic Gulf lies to the southwest. Mount Parnitha is the tallest of the four mountains (1,413 m (4,636 ft)) and has been declared a national park.
Athens is built around a number of hills. Lycabettus is one of the tallest hills of the city proper and provides a view of the entire Attica Basin. The geomorphology of Athens is deemed to be one of the most complex in the world because its mountains cause a temperature inversion phenomenon which, along with the Greek Government’s difficulties controlling industrial pollution, was responsible for the air pollution problems the city has faced. This issue is not unique to Athens; for instance, Los Angeles and Mexico City also suffer from similar geomorphology inversion problems.
The Cephissus river, the Ilisos and the Eridanos stream are the historical rivers of Athens.
The heritage of the classical era is still evident in the city, represented by ancient monuments and works of art, the most famous of all being the Parthenon, considered a key landmark of early Western civilization. The city also retains Roman and Byzantine monuments, as well as a smaller number of Ottoman monuments.