<Li> Caelian Hill (Cælius, Celio) </Li> <Li> Capitoline Hill (Capitolinus, Campidoglio) </Li> <Li> Esquiline Hill (Esquilinus, Esquilino) </Li> <Li> Palatine Hill (Palatinus, Palatino) </Li>

Why were the 7 hills that surround rome helpful to the city's development