Option A is correct: The Ajanta Caves are a series of 29 rock-cut Buddhist cave monuments located in the Aurangabad district of Maharashtra. They are situated in the horseshoe-shaped gorge of the Waghora River.

Option B is incorrect: Sanchi Stupa is located on a hilltop at Sanchi in the Raisen District of Madhya Pradesh. It is situated near the Betwa River, not the Chambal River.

Option C is incorrect: The Pandu-Lena Caves (also known as Nasik Caves) are a group of 24 Buddhist caves carved into the Trirashmi hills near Nashik, Maharashtra. They are not located in the gorge of the Narmada River.

Option D is incorrect: The Amaravati Stupa is located on the banks of the Krishna River in the Guntur district of Andhra Pradesh, not the Godavari River.