A 3D printing project of the famous 12th grotto of Yungang Grottoes -- located in Datong city in Shanxi province -- recently had a watershed moment.

That was when the coloring of the grottoes replica was completed and its final assembly took place in Shenzhen, in South China's Guangdong province -- marking success for the world's first movable 3D print and copy of a cave. 

The 12th grotto of Yungang Grottoes, which was built in the 5th century, is known as the "Music Grotto". The grotto is 14 meters deep, 11 meters wide and 9 meters high. Three-dimensional sculptures in the grotto record the grand performances of ancient musicians. 

The 3D printing project started in March 2017. Over the past two years, the joint project team of the Yungang Grottoes Research Institute and Zhejiang University has overcome difficulties in data collection, processing, structural design, block printing and coloring.

The height of the grotto reaches 10 m while the accuracy of the data collection had to be 0.03 millimeters, said Ning Bo, director of the digital studio of the Yungang Grottoes Research Institute. 

To make the 3D printing Yungang Grottoes exhibition transportable, the team chose light materials and divided the copies of the grottoes into nearly 100 pieces, which were transported in multiple containers. 

The 3D printing grottoes is a 1:1 copy of Yungang Grottoes, which is over 2,000 cubic meters in volume but only five metric tons in weight compared with over 100 tons for the real grottoes, according to Ning Bo. 

After completing the 3D printing, the Yungang Grottoes Research Institute sent an artist team to Shenzhen in March to paint the replica. After 8 months of hard work, a total of 920 square meters of coloring was completed. After the final assembly, the reproduction grottoes are assembled by 110 pieces of 2 sq m blocks, which can be displayed separately or together. 

The 3D printing replica of the 12th grotto of Yungang Grottoes will be unveiled at the Museum of Art and Archaeology of Zhejiang University at the end of December, marking the first stop in world tour.