In a distance 3.5 kilom. northwest of Kos town, at the slopes of a low mount with a view at the coasts of Asia Minor, there is the monumental complex of Asklipio. The space was located in the beginnings of 20th century by the German archaeologist R. Herzog and the research continued later Italian archeologists who attempted, and the restoration of the monument projecting mainly to the Roman side. The complex is extended in three mounds. At the lowest a gallery at Π shape (3rd century b. C) that today is maintained in level of foundation, it encompassed the space from the north,
It is located on Akti Miaouli and it was inside the perimetric wall of the Medieval town and in contact with it. It is the only saved secular building of Knightly period at Kos that was built in 1514 from the Governor (Komentori) of Kos Francesco Sans. Composed by tow arch – covered orthogonal areas. Initially main visage was the westerner (on Mesologgiou street). On Turkish domination the building was used as café and they were two ports opened of the east side (on Akti Miaouli) symmetrical with those of the west side. The east side’s modulation was made on Italian domination.
Other than the imposing Castle and the charm of the old town, a visitor arriving in Kos for the first time will certainly be impressed by the archaeological sites scattered inside the town. According to sources, the homonymous ancient capital of the island was one of the most beautiful coastal towns in the ancient world. The buildings that adorned Kos during the Hellenistic years were the theatre, the prytaneum, the gymnasium and the ancient agora - buildings that served the dual purpose of functionality and decoration. Its perimeter was 4 kilometres with a separate fortification for the harbour. 
The castle of the Knights of the Order of Saint John is situated at the entrance of Kos harbour on what used to be an island in antiquity, communicating with the inland through a bridge that one can still see even today namely the bridge of “Phoinikon" (Palm Trees) Avenue. The castle consists of two defensive precincts. The interior one has four circular towers in the corners; the south-eastern tower forms part of the exterior precinct, which is the larger one of the two, with massive bastions on the four corners, battlements and gun ports.