New lease deal values Seaportâs Innovation and Design Building at $710m Development giant Related Cos. is taking a 50 percent stake in the massive complex. By Tim Logan Globe Staff,Updated December 22, 2020, 4:26 p.m. Email to a Friend The Innovation and Design Building in the Seaport District.David L Ryan/Globe Staff/file The value of one of the biggest buildings in the Seaport District has skyrocketed, with a new investor planning more upgrades to a space that already has undergone about $200 million in renovations. An arm of development giant Related Cos. will take a 50 percent stake in the Innovation and Design Building, a vast complex on the far edge of the Seaport that is rapidly becoming a hub for creative office space. The joint venture with Jamestown â another national developer that operates the city-owned building under a long-term lease with the Boston Planning & Development Agency â values the 1.4 million-square-foot complex at $710 million, according to someone who is familiar with the deal.