This image shows the 15th-century town hall of Leuven (Louvain), Belgium, built in an elaborate late Gothic style with octagonal turrets and much exterior decoration. It is one of the finest civic buildings in Belgium and still exists in the main market square. This negative must be one of the earliest photographs taken of the building. It was taken using the ‘calotype’ or ‘talbotype’ process, invented by William Henry Fox Talbot in 1840 and patented by him in 1841. Calotypes were made by treating sheets of normal writing paper with chemicals to make them highly sensitive to light. The sensitised sheets could be used damp in the camera, where an exposure ranging from ten seconds to over half an hour was necessary, depending on the weather, time of day, intensity of the chemicals employed, and subject. This created paper negatives, which were waxed, as here, to give them translucency. They could then be used to make multiple positive prints by placing them in direct contact with a second piece of light-sensitive paper and leaving both in sunlight. Since paper was used for both negatives and prints, its fibres softened the images and enhanced a painterly effect.