Final answer:
The world's first known urban sanitation system was found at the Indus Valley Civilization, which was more advanced than later systems in London and Rome.
Step-by-step explanation:
The world's first known urban sanitation system was found in the Indus Valley Civilization. This ancient civilization developed sophisticated water engineering and built a comprehensive drainage system with indoor toilets that connected to it. This system ran throughout their cities, showcasing the importance of sanitation in urban areas even in ancient times.
In contrast, other historical systems such as those in London and Rome, while significant, came much later. The Great Stink in London led to the overhaul of the city's sewer system by Joseph Bazalgette, who ingeniously improved waste disposal. Meanwhile, ancient Rome had public latrines connected to the Cloaca Maxima, although it discharged untreated waste into the Tiber River.