One of Glasgow's boldest, most innovative galleries occupies the neoclassical former Royal Exchange building. The modern art, craft, and design collections include works by Scottish conceptual artists such as David Mach, and also paintings and sculptures from around the world, including Papua New Guinea, Ethiopia, and Mexico. Each floor of the gallery reflects one of the elements—air, fire, earth, and water—which creates some unexpected juxtapositions and also allows for various interactive exhibits. In the basement is a café and an extensive library. The exchange building, designed by David Hamilton (1768–1843) and finished in 1829, was a meeting place for merchants and traders; later it became Stirling's Library. It incorporates the mansion built in 1780 by William Cunninghame, one of the wealthiest tobacco lords.