Published by the American Geophysical Union as part of the Field Trip Guidebooks Series, Volume 235. This afternoon trip in downtown Washington, D.C., will permit study of pollution, structural, and other kinds of damage to structures with emphasis on those constructed of fine- to coarse-grained marble but with representatives of limestone and red sandstone. The tour will include in order of examination [date of work initiated (i) and/or occupied (o.) and stone type]: the Renwick Museum (1859o., red sandstone trim replaced 1987), Corcoran Museum (1879c. enlarged 1927, coarse-grained marble), two Red Cross buildings (1915i.–1917o., 1927i., fine-grained marble), Memorial Continental Hall of the Daughters of the American Revolution, DAR (1904i.–1909o., fine-grained marble), Pan American Union Building (1908i.–1910o., coarse-grained marble), Constitution Hall (DAR) (1929o., limestone), Washington Monument (1885o., marble), Jefferson Memorial (1943o., exterior of fine-grained marble), and Lincoln Memorial (1922o., very fine-grained marble). Coarse-grained marble is normally more resistant to pollution damage than fine-grained marble. Direct exposure to the elements hastens degradation. The most severe pollution damage occurs to balustrades and columns: runoff from bronze onto fine-grained marble can also cause serious degradation. Any sort of overhang tends to protect the underlying stone, but exceptions will be seen at the Jefferson Memorial. In general, vertical walls have less pollution damage than horizontal surfaces which can begin to show roughening within two years of installation. Limestone in common use is surprisingly resistant to degradation owing, at least in part, to the porous nature of the stone that inhibits runoff. If one of the trips is made to the Powell Building of the U.S. Geological Survey in Reston, Virginia (1974o., concrete), it will be seen that concrete behaves much like limestone and marble.