As the architecture world mourns Helmut Jahnâs death from a cycling accident Saturday in the western suburbs, the next few months are likely to go a long way toward determining the fate of the 81-year-oldâs most controversial building and his tallest one in Chicago. Jahnâs namesake firm and preservation groups continue working to spare the glassy, spaceshiplike James R. Thompson Center, known for its spectacular 17-story atrium, from the wrecking ball after the state of Illinois recently put the Loop property on the market for sale. Meanwhile, developers are reworking plans to build what would be Jahnâs tallest building in Chicago, a more than 800-foot-tall residential tower on South Michigan Avenue. Construction of 1000M was halted early in the COVID-19 pandemic, just a few months after holding a groundbreaking ceremony and starting work on the foundation.