Because of the natural protection provided by the steep hill, the walls and bastions were constructed at only key places. It was known to be one of the toughest fort that could be captured by anybody in a battle. 
One of the most famous battle associated with this fort is the one fought by Tanaji, a general of Shivaji in 1670. Tanaji and his men scaled a steep cliff leading to the fort with the help of a monitor lizard. At the top, a fierce battle took place and Tanaji lost his life, but won the fort. After hearing about his death, Shivaji said "Won the Fort, lost the Lion". In honor of Tanaji the fort was renamed as "Sinhagad" meaning "The Lion Fort". 
In the above image one can not see the height at which fort is located as the view is obstructed by other hills. The steps to the fort seen in the second are the new additions.
