An armillary sphere is a model of the circles of the celestial sphere, with Earth at the center, the celestial equator and north and south poles. Houston’s version of this sphere is a 72-inch globe set against a backdrop of high-rises in Sam Houston Park. The sculpture has a large vertical ring that represents the meridian of the city. A wide band around the middle of the sphere is decorated with the signs of the Zodiac, and a rod passing through its center represents the Earth’s axis and points up toward the North Star. Elizabeth Bracewell, president of the Houston Heritage Society from 1969 to 1971, donated the sculpture to the city in 1977.