Slated to open on April 29 at the foot of the Great Wall in Beijing's Yanqing district is the Beijing Expo 2019, also known as the International Horticultural Exhibition, and 110 countries and international organizations are expected to participate. 

The Expo will display the latest achievements in horticulture and vegetable farming. Its performing arts center, named "Gui Rui", has been unveiled, after workers completed the building's unique butterfly-inspired roof.

The performing arts center looks like a colorful, dancing butterfly and is one of the expo's icons. 

The center's roof has been covered with an ultra-thin membrane, less than 0.22 millimeters thick and with a light transmittance of 20 to 40 percent, which allows good use of natural light.

Liu Changbao, head of the performing arts center project said, "During this time of year, the temperature in the morning and evening in Yanqing District is relatively low. So we need to choose the best moment and install the membrane when the temperature is above four degrees Celsius and there is no wind."

The center's interior is equally detailed and impressive. In order to show the veins on the butterfly's wings, builders used aluminum alloy to build a chain link net of beautiful patterns on the roof.

During the expo, the center will stage many important activities.

Ye Dahua, deputy director of the Beijing International Horticultural Exhibition Coordination Bureau, said, "During the International Horticultural Exhibition, the performing arts center will stage 2,500 activities, including China Pavilion Day, the opening and closing ceremonies, special days for other countries' pavilions, and special cultural performances from different provinces. It is a good stage to deliver and spread Chinese traditional and modern culture."

Major pavilions and facilities at the Beijing Expo have also finished construction. Together with the beautiful butterfly theater, the event will showcase a splendid blooming world with flora from across the planet.