Traditional Tibetan architecture reflects the innovations of Tibetan craftspersons and the impacts of other cultures. Built of stone, mud, and wood, the buildings are designed to survive high altitude environments when properly maintained. Religious buildings are distinguished by bands of color (usually red) along the upper elements of exterior walls and golden and/or yellow rooftop elements, among other features. Pillars and decorative elements of religious and secular buildings are often carved from wood and painted with motifs that are generally aligned with the function of the space. Like many places around the world, traditional buildings in Tibetan areas are being rapidly replaced by structures of concrete and steel.