The Fortress of Ritzion (Ῥίτζιον) is in modern Darıca in the province of Kocaeli. Ritzion was also the site of a village, landing site, and monastery in Bithynia. All that remains is a horseshoe-shaped tower and an adjoining wall that stretches almost 50 m to the east. The tower perhaps dates to the Komnenian era (most likely to the reign of Manuel I), while the wall seems to date to the Palaiologian era.
The Fortress of Ritzion is located on a hill above the shore at the entrance to the Gulf of Nicomedia near the Cape of Leukatas (Yelkenkaya) around 45 km west of Nicomedia (modern İzmit). It was part of a series of fortifications protecting the main highway leading to the eastern frontier. They also protected ports linked to the south shore, thus the food supply to the capital traveled over these waters. This area of Bithynia (Mesothynia, the peninsula of Nicomedia) retained its strategic military important throughout the entire Byzantine period.
The monastery of Aritzion is mentioned in 1078, though it might appear as early as 787 under a slightly different name. It appears as the port where Manuel Komnenos met his wife in 1160 on his way to an expedition against the Seljuks. Nicholas Mesarites stopped here when he was fleeing Constantinople and heading to Nicaea to elect Patriarch Michael IV Autoreianos in 1208. It is mentioned in the account of the Battle of Pelekanon (1329) as one of the fortresses Byzantine soldiers fled to after Andronikos III was wounded. It became Ottoman after the fall of Nicomedia in 1337, though it briefly regained by the Byzantines in the aftermath of the Timur’s defeat of the Ottomans in 1402, and held until 1421. According to Evliya Çelebi, it was a square fortress with a gate facing the harbor; while it had no garrison in his day, it contained around twenty houses with tile roofs. Its Greek name, Aretsou, survived until 1922, while its Turkish name derives from a form of the Greek name with the definite article. It is currently located on the southwestern corner of Kale Park in the middle of the modern town.
All that remains of the fortress is a horseshoe-shaped tower and an adjoining wall that stretches almost 50 m. to the east. The base of the tower consists of large rectangular blocks, laid with a good deal of filling of broken brick and small stones. The stones of the facing become smaller as the tower rises, until they reach a band of four bricks. The reused bricks are closely set side-by-side, wide mortar bands between them. The rest of the facing consists of small coursed fieldstones with much brick filling and mortar, and similar brick bands at intervals of about 4 m. There are large beam holes located below the brick bands. Some of the mortar has broken away on the east side of the tower, exposing the recessed brick. The tower had a large round inner chamber, which was entered through a passage with a brick vault. It was divided into two levels with a floor supported by large round wooden beams. Embrasures set in arches in the upper chamber faced north and south to cover the adjacent walls.
The interior walls are of large mortared rubble with a good deal of grey surface mortar. The arches of its embrasures are more carefully built, with alternating brick with large stones. A short spur projects from the tower to the adjacent wall, where there is a definite break. The wall, which is 1.85 m thick, has a base of large stones and is faced with roughly coursed rubble with a good deal of brick filling. The inside face of the wall consists of casemates with buttresses separating the individual embrasures. Several blocks at the corner of the street beyond the end of the wall suggest that a corner tower stood here and that the present street pattern represents the original square shape of the castle.
Just at that time he was at the townlet in Bithynia where he had previously settled the captive Romans from Philomilion (Pylai was its name), and he dealt there with envoys who came from the sultan. When he recognized that they had nothing valid to declare, he dismissed them, threatening that, unless they acted in accordance with his will, the Romans' cavalry would shortly overrun their land and pillage everything even worse than now. Having passed some time at Augouste, then setting out from there (at this time a village called Rhitzion by the natives entertained him as he crossed to the farther side [of the Astakenos/Nikomedia Gulf]), he went to the opposite shore. From there he advanced by the road through the coastal cities, and reached Philadelphia; thence, having made preparations, he attacked Turkish territory.
John Kinnamos on Manuel Komnenos in early 1160
Once there I see a ship with a helmsman ... with a cargo of wine jars and other odds and ends .... I suspected the boat might be carrying pirates .... As they were approaching the shore their calls and their strange hairstyle marked them out as foreigners. Pretending to be pleased to see them I addressed them in a friendly fashion. Realising that I wanted to go on board with them, they signalled without any signs of attention or suspicion that I should climb aboard. With a fair wind behind us we came around midday to the port of Ritzion, where to our heart's delight we partook of food. Departing thence we crossed over to Neakomis opposite. It lies on the seashore, preserving scarcely any characteristics of a city. Most of it — it might be more correct to say all of it — has been burned and razed to the ground; buried and reduced to rubble. At Neakomis the houses don't have walls; they are not built with stones and mortar and topped off with rafters [and a roof], but are contrived out of wattle plastered with daub and covered with rushes and reeds. Around the ninth hour of the day I disembarked and set myself down on the beach, offering my thanksgivings to God that he had snatched me from the hand of the foreigner. I did not want to touch any food, though asked to on several occasions by the local townspeople, but prey to sleep I lay there snoring until evening propped up on my elbow.
Nicholas Mesarites, on traveling to Nicaea
Belke, K. Bithynien und Hellespont (Tabula Imperii Byzantini 13)
Foss, C. Survey of Medieval Castles of Anatolia II: Nicomedia
Janin, R. Les Eglises Et Les Monasteres Des Grands Centres Byzantins: Bithynie, Hellespont, Latros, Galèsios, Trébizonde, Athènes, Thessalonique
Dirimtekin, F. “Pelekanon, Philokrini, Nikitiaton, Ritzion, Dakibyza” (Fatih ve İstanbul, İstanbul Fethi Derneği, Cilt 2)
Kinnamos: The Deeds of John and Manuel Comnenus (translated by Charles M. Brand)
Nicholas Mesarites: His Life and Works (in Translation) (translated by Michael Angold)