The Coat of Arms is charged in the center of the flag, and was inspired by an Aztec legend regarding the founding of Tenochtitlán. According to popular legend, the Aztec people, then a nomadic tribe, were wandering throughout Mexico in search of a sign that would indicate the precise spot upon which they were to build their capital. The war god Huitzilopochtli had commanded them to find an eagle perched atop a prickly pear cactus (nopal in Spanish) growing on a rock submerged in a lake. The eagle would have a serpent trapped in its mouth that it had presently snatched. After two hundred years of wandering, they found the promised sign on a small island in the swampy Lake Texcoco. Here they founded their new capital, Tenochtitlán, which later became known as Mexico City, the current capital of Mexico. [ From Wiki ].