The Column of Marcus Aurelius was inspired by Trajan's Column at Trajan's Forum, which is part of the Imperial Fora. Bridges The city of Rome contains numerous famous bridges which cross the Tiber. The only bridge to remain unaltered until today from the classical age is Ponte dei Quattro Capi, which connects the Isola Tiberina with the left bank. The other surviving – albeit modified – ancient Roman bridges crossing the Tiber are Ponte Cestio, Ponte Sant'Angelo and Ponte Milvio. Considering Ponte Nomentano, also built during ancient Rome, which crosses the Aniene, currently there are five ancient Roman bridges still remaining in the city. Other noteworthy bridges are Ponte Sisto, the first bridge built in the Renaissance above Roman foundations; Ponte Rotto, actually the only remaining arch of the ancient Pons Aemilius, collapsed during the flood of 1598 and demolished at the end of the 19th century; and Ponte Vittorio Emanuele II, a modern bridge connecting Corso Vittorio Emanuele and Borgo. Most of the city's public bridges were built in Classical or Renaissance style, but also in Baroque, Neoclassical and Modern styles. According to the Encyclopædia Britannica, the finest ancient bridge remaining in Rome is the Ponte Sant'Angelo, which was completed in 135 AD, and was decorated with ten statues of the angels, designed by Bernini in 1688. Catacombs Rome has an extensive amount of ancient catacombs, or underground burial places under or near the city, of which there are at least forty, some discovered only in recent decades. Though most famous for Christian burials, they include pagan and Jewish burials, either in separate catacombs or mixed together. The first large-scale catacombs were excavated from the 2nd century onwards. Originally they were carved through tuff, a soft volcanic rock, outside the boundaries of the city, because Roman law forbade burial places within city limits. Currently, maintenance of the catacombs is in the hands of the Papacy which has invested in the Salesians of Don Bosco the supervision of the Catacombs of St. Callixtus on the outskirts of Rome. Economy As the capital of Italy, Rome hosts all the principal institutions of the nation, including the Presidency of the Republic, the government (and its single ), the Parliament, the main judicial Courts, and the diplomatic representatives of all the countries for the states of Italy and Vatican City. Many international institutions are located in Rome, notably cultural and scientific ones, such