The Oshakan castle (Aragatsotn district) was first mentioned by the historian Pavstos Byuzand for the first time during the 4th century. The Oshakan was owned by the Arshakians. The Armenian king Khosrov Kotak gave Oshakan as a present to Vahan Amatuni for his valor demonstrated during the emancipated wars of 336.
Mesrop Mashtots was buried there by the wishes of the prince Amatuni. On this grave a small circular church in 442 was constructed. There is information that Mesrop Mashtots established a school in Oshakan. Oshakan with its fruit-bearing gardens was one of the most famous villages of Armenia.
The territory of Oshakan is rich with architectural monuments. On the left bank of the Kasagh River many tombs were excavated. Excavations of the monuments of different eras were found in the various parts of the Didi-Kond hill.
A castle of the 7th to the 5th B.C. century with the 0.25 hectare square was found on the peak of the hill. The walls of that castle sized 2.5 to 2.65 m. in diameter were built from large tuff stones. There is an attic and other buildings inside the castle. The excavation was only for the first and the old part of the five castle complexes situated on the north hill in the 7th century B.C. It consists of 40 rooms, halls and temples. During this time a lot of ornaments, instruments from stone and bone, decorations, idols and more than 100 memorials were found. Discovered within the ruins of the complexes were antique graves of the 3rd century. On the hill, there are more than 1000 graves of the copper century and Urartu period on the east, south and north peak. On the south peak of the hill there are items from the middle Ages - epitaphs, multiple cross-stones. There is also a church named St.Mesrop Mashtots in the center of Oshakan. The hall in the church built by the Catholicos Gevorg IV during the 1875-1879, was also built by Vahan Amatuni in the 443. There is a grave of Mesrop Mashtots under the altar of this church. The church was covered with the icons in the 1960 by H.Minasyan. In the 1884 a bell two-story high, was sanctioned on the eastern side, an original undertaking in Armenian architecture. There is a church of St.Sion built in the 7th century, with pink smooth shaved tuff on the northeastern side of Oshakan at a place known as Mankanots.
There is an original monument of the early Middle Ages 7-8 centuries in Oshakan and the tradition says that it’s ranked the grave of the imperator Mauritius or his mother.
There are church of Tadeos Arakyal, St.Grigory, St.Sargis, St.Astvatzatzin, Tukh Manuk around the Oshakan. On the south from the Oshakan on the River Kasagh was built a bridge from the red smooth shaved tuff by the Catholicos Nahapet in 1706.
There is a monument honor Mesrop Mashtots in the entrance to Oshakan. The monument looks like an opened book and there is Armenian alphabet on the left part of it.