Why is Varanasi considered such an important place for Asthi Visarjan?

Kashi is Moksha-Dayini, the city that grants liberation. It is the eternal abode of Lord Shiva. When the last physical remains (asthi) are immersed in the holy Ganga river within the sacred boundaries of Kashi, it is believed that Lord Shiva himself whispers the Taraka Mantra in the ear of the soul, freeing it from the cycle of rebirth. Maa Ganga, originating from the heavens, washes away sins and purifies the soul. Performing Asthi Visarjan here ensures the departed attains Sadgati (a peaceful state) and moves towards ultimate liberation.