Farringdon Road is a road in Clerkenwell, London. Its construction, which took almost 20 years between the 1840s and the 1860s, is considered one of the greatest urban engineering achievements of the 19th century. Not only was it one of the first engineered multi-lane roads, but it also buried the River Fleet in a system of underground tunnels, solving one of London's most daunting sanitary problems. Its construction also included the building of the world's first stretch of underground railway, a branch of the Metropolitan Railway that later became part of the London Underground running beneath Farringdon Road from King's Cross St. Pancras into the City at Farringdon station.