 When the outer walls were built in the 13th century the main entrance was enhanced . A vaulted corridor led uphill from the outer gate in the northeast . The corridor made a hairpin turn halfway along its length , making it an example of a bent entrance . Bent entrances were a Byzantine innovation , but that at Krak des Chevaliers was a particularly complex example . It extended for 137 metres ( 450 ft ) , and along its length were murder @-@ holes which allowed defenders to shower attackers with missiles . Anyone going straight ahead rather than following the hairpin turn would emerge in the area between the castle 's two circuits of walls . To access the inner ward , the passage had to be followed round . 
 When the outer walls <a href='uninflect' title='1'><mark>were</mark></a> built in the 13th century the main entrance was enhanced . A vaulted corridor led uphill from the outer gate in the northeast . The corridor made a hairpin turn halfway along its length , making it an example of a bent entrance . Bent entrances <a href='uninflect' title='2'><mark>were</mark></a> a Byzantine innovation , but that at Krak des Chevaliers was a particularly complex example . It extended for 137 metres ( 450 ft ) , and along its length <a href='uninflect' title='3'><mark>were</mark></a> murder @-@ holes which allowed defenders to shower attackers with missiles . Anyone going straight ahead rather than following the hairpin turn would emerge in the area between the castle <a href='null_genetive' title='4'><mark>'s</mark></a>two circuits of walls . To access the inner ward , the passage had to be followed round . 
When da outer walls was built in the 13th century tdamain entrance was enhanced . A vaulted corridor led uphill from the outer gate in the northeast . The corridor made a hairpin turn halfway along its length , wit it an example of a bent entrance . Bent entrances was a Byzantine innovation , but dat at Krak des Chevaliers was a particularly complex example . It extended for 137 metres ( 450 ft ) , and along its length was murder @-@ holes which allowed defenders to shower attackers wid missiles . anybody goin straight ahead rather den following the hairpin turn would emerge in thdarea between the castle  two circuits of walls . To access the inner ward , the passage had to be followed round .