It seems to be some kind of unbreakable natural law. In almost any price range except for the very highest, you can choose between an older single-family home on a larger lot and a newer townhouse or condo. This May was no exception, when the Northern Virginia Association of Realtors announced that the median home price had reached $405,000 for Alexandria and Fairfax.

Here in Alexandria, the newest unit was a three-year-old federal townhouse on Beechcliff Drive in Holly Acres. With three stories including a finished basement and two-car garage, it also features three bedrooms, two full baths and two powder rooms. The schools are Hybla Valley Elementary, Sandburg Middle and West Potomac High. Call E-Rae Group at 703-658-2221.

The newest single-family home was a split foyer dating from 1963 on Kidd Street in Mount Vernon Valley. The five bedrooms and two baths stand on a 1/3-acre lot, and the house features newly-replaced windows and siding. The schools are Woodlawn Elementary, Whitman Middle and Mount Vernon High. Call Jose Flores at Weichert, Realtors, 703-360-7400.

While both of these homes display vinyl siding exteriors, the oldest dwelling, dating from 1948, was built of brick in the traditional Colonial style. Located on Spring Drive in Valley View, it also provides the largest lot, at .53 acres, as well as three bedrooms and baths. Call Long & Foster, 301-251-3040.