the.com/mantelpiece

means The shelf or ledge projecting above a fireplace, originally part of the structure framing the hearth, now mostly used for display.

from From 'mantel,' a variant spelling of 'mantle' (a cloak or covering), because the structure draped over and around the fireplace opening like a garment thrown over the hearth. 'Mantel' split off from 'mantle' in English specifically to name this architectural feature — the chimney breast and its ornamental framing — with 'piece' simply marking out the shelf as the part people actually touch, lean on, and clutter with clocks.