A major Harlem site opposite the Metro-North station is about to get the neighborhood’s tallest building.

At 320 feet, 1800 Park Ave. between 124th and 125th streets will soon host 650,000 square-foot twin residential towers that will include 70,000 square feet of retail.

“We can build 320 feet with views of the river and views of the park and it will be extraordinary for the neighborhood,” said Ian Bruce Eichner of Continuum Cos. at a Young Mens’/Womens’ Real Estate Association meeting.

Under the 80/20 program, the development will include about 120 affordable units and roughly 380 market-rate apartments that will rent at about $60 per square foot. Many apartments also will have balconies.

Eichner has hired ODA-Architecture which is known for the quirky cantilevered 100 Norfolk and 15 Union Square West. “The ODA firm has done some interesting stuff,” he said. “This is a 37,000 square-foot footprint right next to Metro-North and it will have two very large towers.”

Despite other air rights available on the block, an area height limit prevents him from adding to the project.

Vornado Realty Trust had held the property, purchased from the New York College of Podiatric Medicine, for a future office tower but demand in the area has not made it cost-effective.

As The Post first reported in April, Eichner picked up the site for $65 million.

“We have the right acquisition numbers and Harlem has had no major development ever,” Eichner said.