A long line forms outside the exhibition at the Palace Museum on Sunday. Visitors had to wait for about six hours to gain entry. [Photo by Zou Hong/China Daily]

The appearance of a rare artistic treasure in Beijing over the weekend resulted in crowds waiting in line for six hours at the Palace Museum, also known as the Forbidden City.

The crowds were eager to see Along the River During the Qingming Festival, the best-known scroll painting in Chinese art history, at the Hall of Martial Valor. The work is sometimes referred to as China's Mona Lisa.

The scroll by Zhang Zeduan (1085-1145), measuring 24.8 centimeters wide and 5.29 meters long, depicts a flourishing landscape in Bianjing－today's Kaifeng in Henan province.

Faced with its huge popularity, the Palace Museum said it would organize another exhibition of the work in 2020, the 600th anniversary of the Forbidden City.

"With growing public demand for exhibitions of national treasures, waiting in line for hours has become routine," the museum said in a statement. "For example, in 2002, when the scroll was displayed in Shanghai, viewers also waited six hours in line."

The work is seldom displayed because of its fragility.

Wang Qi said she drove hundreds of kilometers from Hohhot in Inner Mongolia to visit the exhibition, and it took her most of the day to finally see the scroll. "It was too exhausting, but I still think it was worthwhile," Wang said.

The scroll forms part of a special exhibition titled The Precious Collection of the Stone Moat, which comprises 283 ancient paintings and calligraphy masterpieces once recorded in the Qing Dynasty emperors' catalog.

The display is a main event marking the 90th anniversary of the museum's opening to the public.

Li Geng, 32, from Beijing said he headed to the museum early in the morning. He is a fan of Letter to Boyuan, the only surviving calligraphy from the Jin Dynasty (265-420) with an authentic signature by the writer.

"I arrived only 15 minutes after the opening time. I thought I was there early, but I could see that many people had waited for a long time," Li said. "Even so, I still waited for four hours to enter the exhibition hall. People who arrived after me waited for at least six hours.

"Only 200 people at a time are allowed into the hall, so this slows things down," Li added. "We could linger only for a few minutes because the staff asked people to keep moving to avoid a logjam."

Shan Jixiang, the Palace Museum director, had earlier anticipated huge crowds. "However, we still need to let more people know about the exhibition because it took 10 years for them to have this opportunity," Shan said.

The museum suggested that visitors book tickets online in advance. The scroll is on display until Oct 12.

Li Xiang contributed to this story.