Today, six months after the design for Vessel was publicly unveiled, construction on Thomas Heatherwick’s otherworldly new urban landmark has officially begun at Hudson Yards on Manhattan’s far West Side.

The 150-foot-tall polished steel pavilion will anchor a five-acre public plaza and gardens, designed Nelson Byrd Woltz Landscape Architects, and will comprise 154 interconnecting flights of stairs, 2,500 steps, and 80 landings.