In most parts of Bhutan, the foundation and the main walls of the dzong fortresses, temples and houses are built with stones using a highly skilled masonry. Stone is also used for the surrounding walls and the flooring of courtyards before concrete and asphalt were introduced in the last fifty years. Beside contraction, masonry is also used in making millstones, mortar and pestle, oil presses and sharpening stones. Bhutan does not have a strong tradition of stone sculpture but some people do create stone sculpture of Buddhist iconographical figures and carve prayers and figures on stone slabs and slate. This last art is in serious decline today.