The stupa is probably the most popular monument in early Buddhism and takes its origin from the burial mound. The earliest examples were constructed to store Buddha's ashes and relics. In due course they were built to store the remains of Buddha's famous disciples or holy manuscripts.
The building represents an architectural diagram of the cosmic world and consists of a base, a round drum, a hemispherical dome and a superstructure that consists of a square platform supporting a mast ornamented with a varying numbers of umbrellas gradually decreasing in size.
Although the presented object is a reliquary, it was created with all elements of a regular architectural stupa. The first examples were made with a circular base that later became square like the one under discussion. The umbrellas are a symbol of royalty and thus most appropriate for the crown of such a stupa. The empty cavity once contained smaller metal reliquaries or boxes that held the reliques.
For another reliquary stupa with seven umbrellas see Gandhara: Das buddhistische Erbe Pakistans, Legenden, Kloster und Paradiese, Ch. Luczanits (ed.), Verlag Philip von Zabern, Mainz 2008, p. 174.