A pergola is a structure comprised of two parallel rows of columns, supporting an overhead trellis, or arbor. The columns are not only supports for the overhead structure, they also anchor it. A pergola column would have three main parts: the capital or top part which supports the beams, the shaft which makes up about 80% of the post, and the base which holds the pergola to the ground. The capital may have plain gussets or support wedges, elaborate carvings following the style of the pergola, or plain rings or slabs jutting out. The shaft of your pergola post could have a round or square shape and its surface may be smooth, fluted (with grooves), spiral, or carved into figures or intricate designs. The base would complement the capital with a less elaborate design and may compose the smallest part or be dramatically raised in a similar or contrasting round or square shape as the rest of the pergola pole.