Architecture is also a significant feature of the Bhutanese identity. The characteristic style and color of every building and house in the kingdom is a distinct source of aesthetic pleasure. Dzongs (fortresses), Lhakangs (tremples), Goenpas (monastreies), Chortens (stupas), Palaces, bridges and vernacular housing that can be seen across the countryside from the diverse but harmonious architectural expressions of the cultural heritage and living traditions of the Bhutanese people. The unmatched combination of engineering skill and aesthetic beauty is reflected in all structures. Traditional shapes, colours and patterns makes Bhutanese architecture a class of its own. Among the diverse architecture expressions of the country, the castle-like Dzongs, with their massive stone walls, large courtyards and beautiful architectural details and galleries built on a grand scale without the help of any drawings and constructed entirely without a single nail represent a unique unique architectural marvel. Secular architecture in Bhutan finds its main form in traditional farmhouses. Bhutanese houses have a distinct character from those of other Himalayan countries. Due to steep terrains, they are usually built as scattered houses or in clusters, rather than in rows. Most traditional houses are relatively spacious and take advantage of the natural sunlight. Family dwellings are often three storeyed, with room for livestock on the ground floor, storage and sometimes living quarters on the second floor, while the third floor houses living quarters and Choesham (Shrine). Between the third floor and the roof an open space is usually kept for open-air storage. Boulders over the lath are used to hold down wooden shingles on the roof truss. Windows and doors are normally painted giving the houses a very festive appearance. Floral, animal and religious motifs are mainly used as themes for colourful paintings. The typical construction materials used in traditional Bhutanese houses are timber, stone, clay and bricks.