Why was hadrian famous?

Hadrian was an important leader because he built Hadrian's Wall which showed the northern limit of the empire. He also rebuilt the Pantheon and constructed the Temple of Venus and Roma. He is known to be one of the "Five Good Emperors." This may be because these emperors did not have biological heirs and were forced to pick an heir otherwise, meaning that they could pick someone good for the position instead of have an inept heir replace them.