The sewer is a type of urban public facility that appeared as early as ancient Rome. The prototype of modern sewers originated in Paris, France. Paris still has the largest urban sewer system in the world. Generally speaking, sewer systems are used to collect and discharge domestic wastewater generated in cities and industrial wastewater generated in industrial production. The 200 miles of sewers in Las Vegas in the United States are where thousands of poor people live a hard life in the casino. They picked up some waste from the garbage dump and built a simple "house" to live in. Beds, wardrobes, bookcases, etc. were all found. By 315 AD, there were more than 140 public toilets in Rome. The sociable Romans developed public toilets into places for entertainment and leisure. Just like public bathrooms, for a small fee, people can gather in public toilets and engage in natural behaviors such as gossiping with neighbors, planning parties, discussing politics, or doing business.
Later the Etruscans left to the Romans the most magnificent sewer in the ancient world: the Cloaca Maxima. The Etruscans flourished in central and northern Italy from the 8th to 6th centuries BC. The prosperity of Rome led to their eventual absorption into the Roman Empire. Around the 6th century BC, the Etruscans dug sewers that drained into the Tiber River. The main channel was more than 16 feet wide and was later expanded by the Romans. Seven branches of the sewer flow through city streets and finally merge into the main Maxim Sewer. When storms come, sewers are cleaned by the tremendous force of running water. The Roman scholar Pliny hailed it as Rome's "most remarkable achievement." The sewer is still in use in modern Rome 2,500 years after it was built.