MEXICO // While Egypt has the pyramids of Giza, Mexico harbours the temples of Teotihuacán. Two different cultures on two continents, both ambitiously innovative and way ahead of their time. Even as Mexican ruins go, Teotihuacán is humongous. At its high-water mark, up to 250,000 people lived in this energetic city. Today, four million a year stroll in awe through its haunting remains, along the 2km (1.3-mile) Avenue to the Dead from the ornately carved Temple of Quetzalcóatl to the peerless Pyramid of the Sun, third-largest pyramid in the world.