[3]: 395  To the south, a steep escarpment separates the plain from Simav Mountain, which rises to 1,780 m above sea level.

[4]: 409, 411, 419–20 Simav was historically called Synaus or Synaos (Ancient Greek: Σύναος), also spelled Synnaus or Synnaos (Σύνναος).

In ancient times, it was the main town in Abbaitis, a district in Mysia, and a city in the Roman province of Phrygia Pacatiana.

[3]: 396 The 2013 edition of the Annuario Pontificio puts Synaus in the late Roman province of Phrygia Pacatiana Secumda whose civil capital and metropolitan see was Hierapolis.

[6] In the early 20th century, Sophrone Pétridès placed it in Phrygia Pacatiana Prima, whose capital and metropolitan see was Laodicea on the Lycus.

In the 9th century it was attached to the metropolis of Hierapolis (capital of Phrygia Pacatiana Secunda) and remained so till its disappearance, as appears from the Greek Notitiae episcopatuum.

[10] In 1381, a marriage was conducted between the Germiyanid princess Devletşah Hatun and the Ottoman prince (and future sultan) Bayezid I.

As part of Devletşah Hatun's dowry, her father, the bey Süleyman Şah, ceded several towns to the Ottomans; Simav was one of them.

[11]: 60 The Tapu Defter #438, from the reign of Süleyman the Magnificent, listed Simav as a kazâ in the Sanjak of Kütahya.

[7] Simav has a hot-summer Mediterranean climate (Köppen: Csa),[14] with hot, dry summers, and very cool, wet winters.