There are ruins of a circular stupa shrine at Ambasthala in Mihintale. Only the stupa has been completely renovated—the entourage of Ven. Mahinda met king Devanampiya Tissa at this spot. There had been a stupa called the séla-cétiya erected by King Mahadathika Mahanaga in the first century. King Kanittha Tissa had constructed the circular stupa shrine.  It has been repaired subsequently by the rulers at a later date according to the epigraphical references on the pillars supporting the circular stupa shrine. There are rows of stone pillars around the stupa. The floor of the outer area is lower than that of the inner area. The pillars in both rows measure 4.2 meters each. The roof had rested on these pillars. The stupa found at present is egg-shaped. 

(Heritage of Rajarata by Prof. Chandra Wikramagamage P171)