Ken Griffin’s Citadel, a multinational hedge fund and financial services firm, signed the largest office lease to date at the under construction 830 Brickell, a 55-story Class A-Plus office tower that just recently topped off in Miami’s Brickell Financial District. The firm is taking up 90,000 square feet of space across six floors at the 724-foot-tall tower, which is designed by Adrian Smith + Gordon Gil Architecture with interiors by Iosa Ghini Associati and developed by Vlad Doronin’s OKO Group and Jonathan Goldstein’s Cain International. Construction is expected to complete later this year, anticipated to yield nearly 640,000 square feet of space. Civic Construction is managing construction with Ant Yapi.