The application of the stereomicroscope and compound microscope to the care of historical monuments is discussed. Principal techniques used in architecture conservation are bright field, dark field, polarizing, Zernike phase contrast, interference contrast and fluorescence in transmitted and incident light modes. Practical examples include: paint layer sequences on stucco and plaster from a former monastery at Pfaefers, a 13th cent. medieval roughcast, Scheele-green paint from a 19th cent. window shutter from Lichtensteig and a comparison of a present-day oxide yellow with natural Terra di Siena. -- AATA