Interesting–I haven’t seen those photos before. I remember seeing photos of massive amounts of tulips planted in the garden as well and tulips are well-known symbols of The Netherlands.
I think the ridge is part natural. After all, artifacts were found on that ridge that predate European colonists. But seeing that map in high-resolution makes me think that it was also shaped by humans. It forms pretty neat little 90 degree angles in the corners, which would be pretty rare in nature. Jacobus Van Cortlandt also had Tibbett’s Brook dammed up to make the lake so he was not averse to changing the landscape.
It is a shame that features are built in parks and allowed to just fall apart. The stairs in Brust Park were like this too. Halfmoon Overlook in Spuyten Duyvil was also closed because the stairs were unsafe, I think. They get grants for capital projects so they can build something but the maintenance budget is very skimpy so they can’t keep it up.