Wallachian Plain
The town is situated in southeastern Prahova County, on the border with Buzău County; the four rural localities that surround it are Gura Vadului (north), Baba Ana (south), Săhăteni (east) and Fântânele (west). The Tohani, Pietroasa and Istrița vineyards are all nearby. It is 35 km distant from both Ploiești and Buzău, with Bucharest 92 km to the southwest. Mizil is the only city or town in Romania to lie on the 45th parallel north. Located on a series of fields with altitudes of 80–95 m, it is on the Mizil Plain, a subdivision of the Bucureștilor Plain, in turn part of the Wallachian Plain, and has been called the "gate to the Bărăgan", a reference to the plain extending to its east. It is also on the edge of the plain region and the southern reaches of foothills leading up to the Southern Carpathians, being bounded by the Sărata Plain to the south and by Istrița Hill to the northeast. The area's rocks are Neogene molasse; there is also gravel and sand. Near the surface, there are loess layers of different thickness.