Children take part in a circus performance at a fair organized by Mexico City's government to celebrate the Children's Day, in the main square of Mexico City, capital of Mexico, on April 30, 2015. (Xinhua/Pedro Mera)

A child enjoys himself during an amusement ride at a fair organized by Mexico City's government to celebrate the Children's Day, in the main square of Mexico City, capital of Mexico, on April 30, 2015. (Xinhua/Pedro Mera)

A girl performs a circus exercise at a fair organized by Mexico City's government to celebrate the Children's Day, in the main square of Mexico City, capital of Mexico, on April 30, 2015. (Xinhua/Pedro Mera)

A man and a girl react on an amusement ride at a fair organized by Mexico City's government to celebrate the Children's Day, in the main square of Mexico City, capital of Mexico, on April 30, 2015. (Xinhua/Pedro Mera)

An acrobat makes a circus performance at a fair organized by Mexico City's government to celebrate the Children's Day, in the main square of Mexico City, capital of Mexico, on April 30, 2015. (Xinhua/Pedro Mera)

A child poses at a fair organized by Mexico City's government to celebrate the Children's Day, in the main square of Mexico City, capital of Mexico, on April 30, 2015. (Xinhua/Pedro Mera)