Pandas Tian Tian (L) and Mei Xiang sleep on the rocks in front of their custom-made grotto, In Washington's National Zoo January 2, 2001. Constructed of natural and imitation rock, the grotto resembles a shallow open cave 8 feet wide, 4 feet deep and 5 feet tall, within a natural rock outcropping. Naturally cold now, in the summer this grotto will be cooled by built-in air conditioners. The pandas arrived in Washington from China on December 6, 2000.(CREDIT REUTERS/Jessie Cohen-Smithsonian National Zoological Park)