Xu said quick responses were always needed in answering these questions.

Meanwhile, services provide to visitors have been carefully designed. The staff of the German Pavilion delivered "toilet coupons" to visitors in the long queue, which settled the problem of going to the washroom while queuing, as visitors could return to their original place in the queue after visiting a washroom.

Staff at the pavilion of the Republic of Korea (ROK) handed out bottled water to visitors waiting in the queue. The ROK pavilion is so popular that more than three hours of queuing is needed for a visit.

Volunteers also scattered at Expo Park entrances to hand out fans and maps. Additionally, huge ice cubes were put in buckets beside queues to cool visitors waiting to enter pavilions.

Tu Qiyu, a research fellow with the Shanghai Academy of Social Sciences, said the Expo is a joint effort by both China and the world, as many nations valued this opportunity to present themselves, such as Denmark that is displaying its "Little Mermaid" and Saudi Arabia, which spent an enormous amount of money to build its pavilion. "Even Iceland, which was struck hard by the financial crisis, has made elaborate preparations for the exhibition."

"The world has been condensed into 5.28 sq km," Tu said.

Also on Sunday, Cote d'Ivoire celebrated its National Pavilion day with African aboriginal dances and lively drumbeats. Since May 1, more than 80 National Pavilion Days have been marked to show the charm of these countries, with officials or even top leaders of these countries participating in the events, followed by business delegations.