Nigerian President Umaru Yar'Adua toured China's National Aquatic Center, also known as the Water Cube, on Friday,becoming the first head of state to visit the flagship Olympic venue for water events.

"I'm impressed by the engineering achievements that the Water Cube has made," said Yar'Adua after his visit. "I think all the athletes participating in the Beijing Olympic Games will have the same feeling."

Four and a half years in construction, the Water Cube with bubble-like exterior was completed on Jan. 28.

Previously a chemistry teacher, Yar'Adua was interested in the filtration methods and was told it uses active carbon to filter the water instead of chemicals.

Later Yar'Adua was given an introduction to the National Stadium, or the Bird's Net. He hoped that Nigeria would win seven gold medals in the Bird's Net at the Games in August.

The Water Cube will host 42 Olympic events and the Bird's Nest 47.

Yar'Adua arrived on Wednesday night for a four-day state visit as a guest of Chinese President Hu Jintao. It is Yar'Adua's first visit to China since he assumed office in May 2007. (Xinhua)