The most unique of the Forbidden City's six eastern palaces, the Palace of Prolonging Happiness features an unfinished 20th-century Western-style building with intricately carved white marble facade and cast-iron roof. The palace was built in 1420 and was originally similar in style to the other five palaces before burning down in 1845. Construction of the 'crystal palace' structure standing here today was started in 1909 but was discontinued due to lack of finances.