Roupel fortress
The narrow passage of Rupel is a strip of land formed by the flow of the river Strymonas between the mountains Mpeles and Agistro. It is approximately 11 Km long and its width varies from 500 m to 2 Km.
The fortress of Rupel lies 322 m above sea level having the village of Promachonas at its foot. It is the biggest among 21 groups of fortresses built along the Metaxas line extending to a frontline of 2500 m with 123 active shelters. The battle at the fortress was launched on 6th of April 1941 and finally it surrendered to the Germans on 10th of April 1941 after an order of ceasefire.
Nowadays, Rupel serves more as a monument, a historic sightseeing spot for visitors. Guided tours are offered to the remaining parts of the fortress and in the Museum. For more information, you may contact +302321095102

Istibei fortress
Istibei fortress lies 16 Km north from the village of Neo Petritsi  on the top of mountain Kerkini at an altitude of 1339 m. The distance from the Greek-Bulgarian boarder is 250 m. Along with the fortresses Aspri Petra and Stirigma, Istibei was a base for military attacks to Petritsi, Bulgaria.