See Ambatthala. Geiger thinks (Mhv. Trs.264, n.3) that Therambatthala is the name given to the Ambatthalathūpa, built (on the Cetiyagiri) by Mahādāthika Mahānāga in memory of Mahinda.
But, probably, the whole of this locality later came to be referred to by this name, for Therambatthala is mentioned (Vsm.155, 375; DhSA 187) as the residence of monks, among them, Buddha-Rakkhita and Mahā-Rohanagutta.