Starting from the conventional self-organized arrays of flat Co dots on Au(111), we extended the growth vertically to fabricate Co pillars. The principle is to deposit sequentially a fraction x of an atomic layer (AL) of Co and 1 - x AL of Au. At each step, the deposited Co atoms aggregate on top of the previous dots, increasing their height by 1 AL. Pillars with a 2:1 vertical aspect ratio were achieved. Because of the large number of atoms per pillar, the superparamagnetic blocking temperature is 300 K in the pillars, whereas it is only 20 K in conventional flat dots with the same lateral density.