At the confluence of the Chicago River and Lake Michigan, a long-stalled construction site in the City of Big Shoulders is being transformed into an ambitious new development: 400 Lake Shore Drive, a complex that the developer says will reshape the skyline while showing new ways that supertall buildings can be designed and built. The first of two planned towers is rising on land that formerly was the site of The Spire, a massive twisting residential tower that never got built due to the 2008 financial crisis. Each is expected to stand nearly 900 ft tall. They will house rental apartments—some designated as affordable housing—and offer panoramic views of the city, lake and river from a mix of studio, one-, two-, and three-bedroom units. A plaza between the two towers will mark the end of Water Street. It will feature public art and spaces for residents and guests.…