Rudkhan Castle is a brick and stone medieval castle in Iran. Located 25 km southwest of Foman city north of Iran in Gilan province, it is a military complex which had been constructed during the Seljuk Dynasty. The Castle is built on two tips of a mount, with an area of 50,000 square meters. Its architects have benefited from natural mountainous features in the construction of the fort. The Alborz and its northerly forests became impregnable fortresses for outlaws and sects such as the Ismailis that were seen by the Caliph as heretical. It cuts off a narrow spur to occupy the whole length of a precipitous ridge. Such a position could only be assaulted by trying to starve the defenders out. Preliminary evidence uncovered by digging indicate suggest the foundation of the structure was built in the Sasanian era and rebuilt in the Seljuks reign. Still, there is no precise information regarding the date of its construction. It has been continually used up until the Zandieh Dynasty. Above its front entrance is an inscribed plaque (which has since been removed and is currently on display in a museum in Rasht) stating that the fort had been renovated for the first time between the years 1539 and 1542 for Sultan Hesamoddin and during that time was also known as the Hesami Fort. A river known as `Rudkhan Castle River' also exists near the castle, which originates from the surrounding heights and flows from south to north. After crossing a mountainous winding route with dense forests, the first thing that one notices about the castle is its big entrance gate. The entrance gate is set on the northern wing of the castle and is composed of a gate and two towers on its two sides. On the west side of the Fort lies a main entrance (surrounded by two tall towers), residential quarters, a bath and a running spring passing through. This spring was the main water source for the Fort and following an earthquake in Gilan it ran dry, although since then it has been resurrected thanks to the efforts of Iran’s Cultural Heritage Organization. The east side of the Fort is a bit smaller and has more military characteristics. It consists of two towers, another entrance, a prison and an emergency exit. Above the north and south walls are a number of octagonal areas and the deliberate cracks in the walls of them are assumed to have been for monitoring the adjacent area and shooting arrows at approaching troops. Though being threatened and even partly eroded by excessive humidity and vegetations rooting in the chinks of its old but lofty walls, Rudkhan castle is still in very good condition as compared to other castles of the same era.