It's Harihar Fort, situated about 40km from Nashik, Maharashtra, India. It was built during the Seuna (Yadava) dynasty, it was later seized by the Mughals in 1636, underscoring its strategic importance. The fort is famous for its rock-cut staircase—a narrow, nearly vertical climb that rises 60m with 117 steps carved into cliffside, challenging even the most seasoned climbers. This design was a deliberate choice to make any approach perilous and slow, offering a clear advantage to its defenders. While its strategic role is evident, specific details about exactly who constructed it are still unknown.