The Aztecs, like other Mesoamerican peoples before them, devised a form of writing to record important events and other aspects of their culture: they chronicled their history, genealogies, and the lineage of rulers; they recorded land distribution, population counts, tribute payments, and laws by which they lived; and priests kept sacred books dealing with gods and the religious ceremonies honoring them. Aztec writing was based on a system of signs and symbols, some pictographic, others ideographic, and some incorporating phonetic elements. The glyphs represent the names of people, events, and places and served as mnemonic devices helping the reader to fill in information from memory. Place-names were the most common type of Aztec glyph. The front of this block, divided into quadrants, features four glyphs: in the lower section are the Aztec name-glyphs for the towns of Cholula and Tula. Cholula, or Cholollan, in Aztec times was called tlachiualtepetl, meaning "hand-made hill," a reference to the ancient man-made pyramid at the site. The identifying glyph is a mound with a trumpet inscribed on it. The glyph for Tula, or Tollan, meaning "place of the reeds," is a "lake" with stylized reeds growing from it. It is possible that the two upper glyphs represent early colonial versions of the place names: Cholula as the hill with a cross atop standing for the church the Spaniards built on the pyramid, and Tula as a bell tower incised with a small cross on the bell.