Ancient Rome was built upon seven hills, which are now scarcely discoverable on account of the vast quantities of rubbish with which the valleys are filled. Pliny estimates the circumference of the city in his time at 13,000 paces (which nearly agrees with modern measurements), and the population at 3,000,000. Rome was filled with magnificent public edifices, temples, theatres, amphitheatres, circuses, naumachiæ, porticos, basilicæ, baths, gardens, triumphal arches, columns, sewers, aqueducts, sepulchres, public and private palaces, etc.