The following instructions refer to the construction of a bowl or lower hemisphere. A dome (or upper hemisphere) is obtained by the exact opposite procedure.
You start with a closed square, hexagon or octagon made of flat Bioblo blocks. The blocks of the second layer are placed so that their ends are above the centers of the blocks below.
TIP: The yellow and ochre building in the centre of our Bioblo panorama is a good example of a spherical building. The building on the far right, on the other hand, shows how a bowl-shaped construction can be used (click on the picture for the high-resolution version):