Students at Boston's Northeastern University kicked off the spring semester last week in a new 234,000-square-foot science and engineering building designed by local firm Payette. The six-story Interdisciplinary Science and Engineering Complex includes labs and classrooms organized around a central atrium, which the firm describes as the building's "cultural melting pot." Judging by the reaction on Twitter, the atrium and its spiral staircase appears to be one of the stars of the new complex.