Boston Properties Inc. has completed the acquisition of Bay Colony Corporate Center in Waltham for $185 million.

The final purchase price consisted of approximately $41.1 million of cash and the assumption of approximately $143.9 million of indebtedness. The assumed debt is a securitized senior mortgage loan that bears interest at a fixed rate of 6.53 percent per annum and matures in June 2012. The loan requires interest-only payments with a balloon payment due at maturity.

Bay Colony Corporate Center, a one-time trophy asset in Waltham, ended up becoming one of the most prominent faces of the commercial real estate bust. The property was put up for sale by its fourth owner in three years.

In June, Banker & Tradesman reported that brokers and investors surveyed pegged Bay Colony’s current value anywhere between $150 million and $185 million. It was thought that a bidding frenzy could push the purchase price north of $200 million.

The real estate arm of Prudential Insurance Co. seized Bay Colony from prior owners Eastern Real Estate through a mezzanine debt foreclosure. Eastern and Prudential split ownership of the property’s total $125 million in mezzanine debt, with Prudential owning a more senior $75 million slice. It converted this debt into equity and ousted Eastern last year.

Bay Colony Corporate Center has approximately 1 million square feet and is a Class A office park, according to a statement. The four-building office park sits on 58 acres and has views of the Cambridge Reservoir, Waltham and the Boston skyline.