In architecture, a
1 a : the lowest member of a base : subbase b : a block upon which the moldings of an architrave or trim are stopped at the bottom. 2 : a usually square block ...
a heavy base supporting a statue or vase
A block or slab on which a pedestal, column, or statue is placed. 2. The base block at the intersection of the baseboard and the vertical trim around an opening .
If a building has columns, you can call the platform or base on which a column