 Its topping-off day Tuesday for The Spiral, Tishman Speyers 3.7 billion, 66-story Hudson Yards District skyscraper, beribboned with a band of cascading, landscaped terraces and hanging gardens. Its a milestone for the 1,041-foot-tall tower and for Tishman Speyer PresidentCEO Rob Speyer, who steered the project from the outset. 