Mt. Moriah
What is so special about Mt. Moriah that would cause Adam, Noah, Abraham, Issac, Jacob, Moses and Aaron to all build altars there?
Since Mount Moriah was a common land mark that all people would know, it would make sense that they would use it frequently in stories, especially when they where hilltop dwellers. But as for spiritual significance, El-Shaddai means "god of the mountain" so they probably sacrificed on the closest mountain around.