Another view of the Block House No. 4 and the exposed manhattan schist face where West 123rd Street was cut through at the northern termination of the park. As we’ve seen in this story, the geology and resulting dramatic topography of a ridge of Manhattan Schist is a defining feature of Morningside Park. In fact, it’s only due to the daunting nature of this rock that Andrew Haswell Green decided to not extend the east-west street grid through this part of Manhattan and instead called for a park to be designed and constructed on this land.