One of the biggest private equity firms is turning into a huge real estate company

The biggest private equity investor in real estate is making yet another multi-billion dollar buy.

Blackstone's seventh real estate fund is spending about $6 billion to buy Strategic Hotels, the latest in a series of big acquisitions and sales by Steve Schwarzman's PE firm in 2015.

Strategic's shares were up about 4% at the open Tuesday morning September 8.

The company's shares plummeted in the wake of the financial crisis and have steadily risen in the time since, but never fully recovered. Blackstone's offer for Strategic represents a premium of about 13% based on the company's share price before news broke in late July that the firm's real estate fund was looking to buy it.

Tyler Henritze, co-head of U.S. acquisitions for Blackstone Real Estate, said in a statement "We are excited about the opportunity to acquire one of the highest quality luxury hotel portfolios in the U.S."

The deal represents yet another big property deal for Blackstone. The company went on a real estate buying spree after the financial crisis, ending up as the largest private sector landlord in America.

Real estate contributed more to Blackstone's bottom line than private equity in 2014, making up 43% of the company's economic net income, according to Greg Roumeliotis and Mike Stone at Reuters.

It has continued striking deals in 2015. The firm in April agreed with Wells Fargo to purchase most of the assets of GE Capital Real Estate in a transaction valued at approximately $23 billion.