Workers are busy assembling a horn-like "sunny valley" along Expo Boulevard on Wednesday, December 17, 2008 - which marked the start of the 500-day countdown to the opening of the 2010 Shanghai World Expo. Composed of steel and special plastic film, the "sunny valleys" can direct sunlight into the underground level of the Expo Boulevard, which is the central axis of the Expo Park and links the park's four major venues and two Metro lines. Six of these structures will be built along the 1-kilometer boulevard. [Shanghai Daily]