The Volkhov and the Neva Rivers were constituents of major trade routes since prehistory, and their banks are dotted by archaeological sites. Staraya Ladoga has a number of pre-1700 sites, including two of about a couple of dozens standing pre-Mongol churches in Russia. Both of them were built in the 1160s. The Oreshek Fortress in Shlisselburg and the Koporye Fortress, both built in the 14th century, and the Ivangorod Fortress, originally built in 1492, are excellent examples of Russian fortification art. Podporozhsky District contains the best samples of wooden ecclesiastical architecture in Leningrad Oblast, some of which are collectively referred to as "Podporozhye Ring": The Resurrection Church in the settlement of Vazhiny, the Saint Nicholas Church in the village of Soginitsy, the Sts Peter and Paul Chapel in the village of Zaozerye, and the Saint Athanasy chapel in the village of Posad. The two other notable wooden churches are located in the villages of Gimreka and Shcheleyki close to the Onega Lake shore. The center of Vyborg preserves many examples of medieval Swedish architecture, unique for Russia.