Standing on the High Line last week while surveying the twisted concrete structure rising out of the ground for his latest building, the XI, the architect Bjarke Ingels said, “It’s a lot more dramatic in real life, huh?”

His client Ziel Feldman, the chairman and founder of HFZ Capital Group, said with a smile, “You’re not changing your mind, are you?”

Mr. Feldman knew it was already too late for major changes. Construction is well underway on the XI (the Eleventh), a mixed-use development at 76 11th Avenue that is transforming a full city block between 10th and 11th Avenues, and West 17th and West 18th Streets, directly south of the Frank Gehry-designed IAC Building.