The one in the middle.
"Emerald Plaza’s hexagonal design allows for the maximum number of guestrooms and offices with views, as well as minimizes wasted space typical to rectangular buildings. Further more, this design utilizes angled window sills, which reflect ambient sunlight into the building, reducing lighting requirements. The Emerald Plaza was built in 1990 at a cost of $150 million. It consists of a steel frame structure with an exterior combination of granite stone panels and reflective glass set in a custom Kynar green aluminum window framing system. The structure itself is balanced on a 9-foot deep concrete block which acts like a floating device, allowing the building ebb and flow, mimicking the movement of water. This technique makes it one of the most stable structures in San Diego."