Those "layered palaces" have gone, and the beauty depicted in the scene has been lost to time, but the cultural relics on display at the exhibition can still transport visitors to this distant and wondrous horizon.

The largest of them is a 1.5-meter pottery roof figure, an architectural component used to decorate the ends of rooftop ridges. It is a chiwei (literally "an eagle's tail") and is shaped to resemble a hovering eagle overseeing the top of the palace.

"This alone allows you to imagine how grand the original palace was," Feng says. "A lot of palace architecture had such large chiwei pieces back then, and they were connected to each other in rows. What a splendid sight it must have been."

Li Shimin was proud, but he also had fears. Folk legend often claimed that as he got older, he regretted seizing the throne at the cost of lives. To keep the demons of guilt at bay, he hung portraits of two of his trusted generals Qin Qiong and Yuchi Jingde over the front gate. The act is said to be why portraits of the two generals are viewed in China today as "gate gods" and are put up to protect homes.

It is perhaps difficult to be sure how credible this anecdote is but one epigraph on exhibit may be an indication of the high esteem in which the emperor held Yuchi, who despite his birth status as a commoner, was buried in the imperial mausoleum to protect the emperor forever. The epigraph, written in a script known as feibai ("the flying white"), a noble writing style favored by Li Shimin, is the only ancient epigraph written in the style found so far in China.

"Recognizing and appointing capable people, accepting advice with an open mind, Li Shimin created the template of benevolent governance with loyal ministers," Feng says.

To expound on this political legacy, the National Library of China has also contributed precious ancient books to the exhibition. For example, a 14th-century edition of Zhenguan Zhengyao (Essentials About Politics From the Zhenguan Reign), a compendium of statecraft compiled by Wu Jing, a historian during Li Shimin's time, is displayed near the entrance.

"The book documents disputes, discussions, admonitions, and advice both from Emperor Taizong and his high officials," Zhang Zhiqing, deputy director of the national library, says. "It is a monumental work on ancient Chinese political theory, strategy and practice.

"Visitors to the exhibition can also do some extra reading to explore the historical wisdom contained in the ancient classics," Zhang says. "That will provide them references in a modern context."