Rreef's acquisition might only be the tip of the proverbial iceberg. A source tells GlobeSt.com that Rreef has picked up "some, but not all, of the properties" in the portfolio. Calls to Rreef's Chicago office and Hines' Boston office were not returned by deadline. Cushman and Wakefield declined comment.

Developed between 1984 and 1986, Riverfront Office Park is a twin-tower facility which consists of two buildings, the 14-story One Main St. and the 18-story 101 Main St. The facility features a 646-space parking garage, and building amenities include a conference center, cafeteria and fitness center.

The sale price would appear to represent a large-scale loss for NOP, which purchased the park in October 2002 for $213 million, but the declining Cambridge office market may have contributed to the drastic drop-off in the pricing. At the NAIOP-SIOR annual forecast meeting held Thursday, Spaulding & Slye principal Debra Gould said that she did not expect the 25% office vacancy rate in Cambridge to change "for 12 to 18 months."

One source familiar with the situation concurred, "They bought it at the height of the market, and they paid full price. This is going to be a big loss for them." National Office, a joint venture between Hines, the international real estate firm, and the California Public Employees Retirement Fund, does not appear to be shying away from the Greater Boston office market. The JV recently purchased Wellesley Gateway, headquarters of Harvard Pilgrim Healthcare, for $70 million. The 270,000-sf, first-class office space is located along the Route 128 corridor, just 10 minutes from Boston.