Chicago’s Merchandise Mart plays host to hundreds of thousands of visitors a year, rushing through the lobby on their way to various events and tradeshows. What many never notice are the 17 murals celebrating global commerce that line the lobby walls. Installed in 1930, the murals are the work of Jules Guerin, whose paintings also grace the Lincoln Memorial and Penn Station. Recently, three conservation experts have brought the murals back to life. As one of the overnight security guards noted, “It’s amazing what three people and some Q-tips can do.”