"Originally the area of the Forum was wet and covered in grass, as it was not suitable for building. A necropolis has been found, dating from the 10th century BCE, but otherwise the area doesn't seem to have been used. This changed in the 7th century with the construction of the Cloaca Maxima. This sewer system, which was enclosed and covered to drain the areawas based on a natural stream, was a sign that the settlements on the Palatine Hill was spreading into the valley." - Rome-Italy.org.uk.