Architecture structure and mold piece for forming a cave in surface of architecture member

The subject application relates to an architecture structure and a mold piece for forming a cave in the surface of an architecture member. The architecture structure comprising: a plurality of molds, the molds and a base collectively defining a space for grouting concrete therein; a rebar cage disposed within the space for grouting concrete, the rebar cag including a plurality of main rebars and a plurality of stirrups surrounded around and fixed to the main rebars; an insert having a body of substantially cylindrical shape and an open end, the insert being fixed to one of the main rebars or the strirrups, wherein the open end has an opening facing to the molds or the base; and an mold piece having a first end and a second end opposite to the first end, wherein the mold piece is arranged so that the first end of the mold piece removably attaches to the opening end of the insert and the second end is against a corresponding mold.