Cloud 9 is an exploration of three-dimensional city. It blurs boundary between ground and building by interwoven of shape and space. The building becomes part of urban landscape, and the terraced roofs become the extension of ground surface. By lifting and undulating the outer façade, enlivens the corner of streetscape and makes private and public space blend with each other. The continuous undulations and terraced roofs connect sky gardens and courtyards. Penetrations of the volume, allows wind flow and improves micro-climate. Layers of vegetations make Cloud 9 a green place for office crowd.