Ternopil Oblast is an oblast (province) of Ukraine. Its administrative center is Ternopil, through which flows the Seret River, a tributary of the Dnister.
One of the natural wonders of the region are its cave complexes. Although Ternopil Oblast is among the smallest regions in Ukraine, over 100 caves have been discovered up to now. Scientists believe that it is only 20% of all possible caves in the region. The biggest cave is Optymistychna Cave. Measuring 230 km (140 mi) in total length, it places the cave in first place in length among caves of Eurasia and the fifth in the world ranking. Twenty percent of the land in the region is chornozem soil.
Ternopil Oblast is accounted for some 34 castles. The most prominent one is the Zbarazh Castle. Its fortifications alone expand over 16 ha (40 acres). In the summer of 1649 the castle was the epicenter of a standoff between troops of Bohdan Khmelnytsky and the army of the Polish-Lithuanian Commonwealth. These events were later described in the novel "With Fire and Sword" by Polish Noble Prize recipient Henryk Sienkiewicz.
It is here where Dniester Canyon passes through, and is considered one of the wonders of Ukraine stretching for 250 km (160 mi).