SL Green Realty Corp. acquired 635 Sixth Avenue and 641 Sixth Avenue, two adjoining New York City buildings totaling 267,000 sq. ft., from Atlas Capital Group LLC for $173 million in an off-market transaction. The price works out to $648 per sq. ft.

The buildings were built in 1902 as a contiguous department store spanning a full block on Manhattan’s Sixth Avenue. 635 Sixth Avenue contains 104,000 sq. ft. of space and recently became vacant after Apex Technical School moved out. 641 Sixth Avenue contains 163,000 sq. ft. and is 100 percent occupied, by tenants including Google and Infor. The buildings also contain 47,000 sq. ft. of combined retail space. Atlas originally bought 641 Sixth Avenue in 2007, and recently acquired 635 Sixth Avenue for full block assemblage.

“First the acquisition of 304 Park Avenue South and now the addition of these two properties are classic SL Green-type investments—sourcing off-market transactions, fully understanding their complexities, underwriting their potential and then executing,” said SL Green President Andrew Mathias in a statement. “This is a great example of how we utilize our extensive relationships and know-how to capitalize on opportunities.”

Rob Martin, of Jones Lang LaSalle, served as an advisor on this transaction.