First record about Porkhov fortress was made in Novgorod's chronicles in 1239. Knight of Novgorod Alexander Jaroslavovitch ('Nevsky') established the trade way along Shelonj river from Novgorod to Pskov by building of small wooden strong points. Porkhov fortress was one of them. Its fortifications consisted two lines of earthen ramparts and ditches and wooden wall above the ramparts.
In 1346 Great Lithuanian knight Olgerd invaded the Novgorod's territory and took by storm fortress Luga and Shelonj and sieged fortress Opocka and Porkhov. Porkhov stood it's first test. Lithuanians got the war indemnity in 300 rubles from the fortress and got away. In 1387 new stone fortress was erected on the right bank of Shelonj river. The fortress had four towers. Towers had 15-17 meters height and 4-6 wooden levels and walls had 1.4-2 meters thick and 7 meters height. The towers pushed out from the wall's line and could flanked the approaches to the walls. All building works were finished within a year.
July 1428 Lithuanian knight Vitovt besieged the fortress. It was the first siege in Russia with mass artillery shelling. The fruitless siege endured 8 days and fortress was badly damaged. In 1430 the big reconstruction was in the fortress. Thick of it's walls was increased considerably up to 4.5 meters at the most dangerous parts. The gates of the fortress were reconstructed too - the portcullis were arranged.
After seizing the Novgorod and Pskov territories by Moscow in 1478 and 1510 the state border was moved to the west far from the fortress. There were not any storms and sieges of Porkhov from this time. It's fortifications lost it's value soon and preserved till nowadays not disturbed by later rebuilding and reconstructions.
The trade city appeared near to the fortress. In 1776 it became the area administrative center. Rapid city growth begun in 1890s after the railway Pskov-Dno was built. The fortress ruined gradually as long as some repair works were held in 1912.
During the WWII Porkhov fell under German occupation for 4 years. Nikolskaya church in the fortress was in action during the war. It's abbot father Pavel was linked with partisans and provided shelter for escapees from German POW camps. February, 1944 German troops burnt the city and gone away.
Now Porkhov is one of the small Russian provincial cities. There few old city buildings preserves. The fortress is restored partly. The wall along river bank is reconstructed and could be observed, but towers are still in the ruined condition without roofs and floors and could be visited only by your own risk. There are the little local museum and nice botanic garden inside of the fortress. Nikolskaya church which was closed in 1930-th is on the duty now.
References:From its origin as a small stronghold built by the ancient Illyrian tribe Dalmatae, becoming a royal castle that was the seat of many Croatian kings, to its final development as a large fortress during the Ottoman wars in Europe, Klis Fortress has guarded the frontier, being lost and re-conquered several times. Due to its location on a pass that separates the mountains Mosor and Kozjak, the fortress served as a major source of defense in Dalmatia, especially against the Ottoman advance, and has been a key crossroad between the Mediterranean belt and the Balkan rear.
Since Duke Mislav of the Duchy of Croatia made Klis Fortress the seat of his throne in the middle of the 9th century, the fortress served as the seat of many Croatia"s rulers. The reign of his successor, Duke Trpimir I, the founder of the Croatian royal House of Trpimirović, is significant for spreading Christianity in the Duchy of Croatia.