Interesting difference in value of commercial properties between Fairfax County and urban Washington, DC
The media coverage of the sale of the old Mobil Oil Company campus on Gallows Road in Fairfax-- 117 acres, 1.2 million square feet of buildings, 2,850 underground parking spaces---reports that the property value of the site is $193 million according to State of Virginia and Fairfax County tax records ("Inova plans medical research complex in Fairfax," Post).
The PNC Place office building in Downtown Washington has about 365,000 square feet of usable space.
In DC, one office building is often worth more than that. A typical city block (although they do vary), is about 1.5 acres in size.
The Mobil Oil campus is about the same size as 78 of DC's city blocks, which would be a significant chunk of the Downtown.
According to the Washington Business Journal ("A new milestone: D.C. joins the $1,000-per-square-foot club with sale of PNC Place"), the building at 800 17th Street NW is worth double the value of the 117 acre Mobil Oil campus in Fairfax County.
Although granted, assessment value and sales value often differ.