Zheng took a total of seven trips from China to India, the Middle East, South East Asia, and Africa with his large fleet of ships, manned by up to 30,000 sailors and marines. The voyages were diplomatic missions, and were able to bring back exotic plants and animals from distant lands. (i.e. giraffes) The flagships of the fleet were "treasure ships," huge vessels that reached up to 400 feet in length.
The Earth and Its Peoples A Global History, Bulliet et al., 2005.