The houses are divisions of the ecliptic plane (a great circle containing the Sun's orbit, as seen from the earth), at the time and place of the horoscope in question. They are numbered counter-clockwise from the cusp of the first house. Commonly, houses one through six are below the horizon and houses seven through twelve are above the horizon, but some systems may not respect entirely that division (in particular when the Ascendant does not coincide with the first house's cusp).