Lambsar or Lambesar is one of the largest and the most fortified castle of Ismailis (Assassin) in Iran. The fortress located in central Alburz mountains, south of the Caspian Sea, about 120 km from present-day Tehran. Labesar is located in the northeast of Razmian village (the central district of Roodbar e Shahrestan). Only ruins remain of this magnificent fortress today. Very deep valleys surrounding the fortress make it impossible to access from the East and West sides.The North and South fronts are the only possible ways to get in the fortress. Although slope of the mountain with a difference of 150m on both levels is stretched from north to south with the length of 480m, the castle is more than 190m in width. The two-layered huge parapets made up of very large stones which are 10m high, along with the main building in the north of the fortress with cut stone walls which are 1.2m wide, wonderful water reservoirs and grain stores in south and southeast of the castle, towers and water supply system are among the characteristics and features left from Lambesar fortress which perplex the visitors. In the North side of fortress a huge building with 4 smaller extensions remained which face to the East.
Final days of Lambesar:
The Ismailis forts were the last line of defense against Mongol aggression in Persia. Mongols had a hard time to conquer Ismailian's forts. Hulaku Khan was disappointed of his commanders therefore he took over an army of 10000 soldiers and moved toward Alamut. In 1256 AD after a couple moths Meymoon-Dej fort surrendered to Hulakus army, and Imam Ruknud-Din Khurshah captured. Hulaku Khan asked Ruknud-Din Khurshah to order his followers to surrender, but Lambesar fort, Gerd-kouh fort and Alamut fort did not follow the order. Finally after a year of surrendering, in 1257 A.D cholera epidemic took many lives in Lambesar and caused Mongols to succeed. Hulaku ordered to ruin the fort and beheaded whoever survived from deadly disease. In 1275 A.D and again in 1389A.D,small groups of Ismailis who had survived the Mongol invasions attempted to recapture Alamut ,but their attempts were shortlived.