In its developed stages Greek *architecture was based on the use of finely dressed stone masonry, predominantly limestone. Where available either locally or transported, white *marble was used for the finest structures. The coloured marbles favoured in the late bronze age were not used. Transport costs were a major factor in the availability of stone: local stone would often be used as an economy and this occasionally tends to the use of abnormal materials such as trachite at *Pergamum. In major buildings the dressed blocks were regularly fastened with clamps and dowels of wood or metal, but without mortar; and although exceptionally almost entire buildings might be of marble, including ceilings of quite large span (e.g. the *Propylaea at Athens), considerations of cost frequently meant that the less conspicuous parts were built in local limestone. See quarries. Inferior materials were regularly surfaced with fine marble stucco to resemble masonry, but the use of fine marble veneer was a Hellenistic innovation, as was the reintroduction of coloured and patterned marbles (other than grey). In some Hellenistic buildings such decorative stone facings were imitated in painted plaster and all but the best materials were plastered on the interior often to receive painted decoration (see painting (techniques); painting, greek).