The term UNDERGROUND LOCALE can be solved by the 6 letter word LONDON. London is the capital of England and is one of the most populous cities in the world. It is home to the iconic London Underground, a rapid transit system that serves the city and its surrounding areas. The London Underground is the oldest underground railway network in the world, having opened in 1863. It consists of 11 lines and 270 stations, making it an important part of the city's infrastructure.