The Roman Empire spanned over 1/9th of the Earth's surface and ruled over a quarter of humanity across three continents at the height of its power. Roman architecture and town planning had a lasting legacy. They developed advanced building techniques like concrete and the arch, which enabled massive structures like the Colosseum and aqueducts. Roman towns were planned with gridded streets and usually centered around a forum. Notable architectural achievements included amphitheaters, temples, bath complexes, and the iconic Pantheon dome. Roman dress varied by class, gender, and occasion, with tunics and togas for citizens and more elaborate versions for elites.