The adjacent provinces are Kocaeli to the west, Bilecik to the south, Bolu to the southeast and Düzce to the east.

It is one of the paradise-like spots of the country with its sea, beaches, lakes, rivers, highlands, thermal springs, traditional Ottoman lifestyle districts such as Taraklı and Geyve and noteworthy historical relics that are inherited from the Byzantine and the Ottoman eras.

The Native Muslims are Armenians and Greeks who gradually converted to Islam, and it should not be ignored that Turk households settled in the region.

Adapazarı was a district of Kocaeli for many years but separated from it and took the name of Sakarya on June 22, 1954 by Law 6419.

Adapazarı took the name of Sakarya since it was the centre of the districts f Akyazı, Geyve, Hendek and Karasu.