At the center of this historic, tree-filled public square, atop a 70-foot-high outcrop of Manhattan schist (the same bedrock that anchors our skyscrapers) stands a 47-foot cast-iron watchtower (Julius Kroel, 1865), the last remnant of a citywide network used to spot and report fires in pretelephone days. Around it, an Acropolis provides great views of Manhattan, and of the handsome neoclassical row houses of Mount Morris Park Historic District,which extends west from the park.