Vahalkada and Vatadage

A vahalkada is an ornamental frontispiece built out from the base of a stupa at each of its four cardinal points, densely carved with figures, animal friezes and guardian stones - Mihintale and Kelaniya have well-preserved examples. A vatadage is a different structure entirely: a circular building erected around a smaller stupa to shelter it, with concentric rings of stone columns that would originally have supported a roof, as seen at Polonnaruwa and Medirigiriya.

The two are easy to confuse by name alone, so the reliable way to tell them apart in an answer is by function: a vahalkada decorates and marks a stupa's face, a vatadage protects and encloses one.