Why do mosques have domes?

Although most mosques feature domes, the dome is purely a decorative and traditional architectural structure with no symbolic or other spiritual meaning, according to About.com. Other mosque parts, such as the minaret, have more spiritual significance.

The interior of the main dome of many mosques falls directly above the prayer hall and is adorned with patterns or other images. In addition to one or more domes, mosque architecture also features a minaret, a tall, slender tower with a balcony. The minaret is spiritually significant as the high point of the mosque that is seen from a great distance. Historically, the balcony provided a place for the muezzin to call the people to prayer.