Kresna Gorge (Bulgarian: Кресненско дефиле) is a steep valley in south-western Bulgaria, stretching about 18 km. The gorge has been formed by the Struma River, which flows from the Vitosha mountains. Kresna gorge has a rich biodiversity, which has come under pressure from the Struma motorway construction project, a new leg of the Trans European Corridor No. 4. In the south, the gorge bisects the Tisata nature reserve. Kresna Gorge was the place of the Battle of Kresna Gorge between Bulgaria and Greece during the 1913 Second Balkan War. The Greek army was threatened by encirclement in the valley, but due to the Romanian army advancing against the undefended capital Sofia, Bulgaria had to agree to an armistice and the resulting peace treaty in Bucharest which was unfavorable to Bulgaria’s territorial aspirations.
Source: Wikipedia