The so-called three-world system is a prominent one in Buddhist thought. The ancient Theravāda Buddhist (see Theravāda Buddhism) tradition saw a flat world with Heaven above and Hell below. Later, a ten-thousand world vision emerged, and still later Buddha fields, where true wisdom is taught. Such a field is the “Pure Land” of Pure Land Buddhism (see Pure Land Buddhism). The Buddhist cosmology also contains the ideal of nirvāna (see Nirvāna), which, like the Pure Land, is a state of being rather than a particular place.