Extell's 1520 First Ave. under construction in August 2024The just-completed tower at 1520 First Ave. is poised to be the first ground-up medical office tower in the borough in decades. “1520 is definitely top of the market,” said Elliot Dennis, founder and principal broker of medical office specialist Dennis Healthcare. It's the first one of its kind in a very long time.”Barnett put together the assemblage for the 30-story, 425K SF medical office building in 2018. And its 6K SF tower floors, from 18 through 30, are seeking $125 per SF. The UES is primed for new medical space like Extell’s development, Dennis said.