From the BBC:

Algae and sludge deposits built up over years are being removed from the original Roman lead-lined floor of one of Bath's top tourist attractions.

The Great Bath at the city's Roman Baths has been drained of natural thermae spa water for the clean-up.

The site, below the modern street level, is one of the best examples of a preserved Roman bath complex in Europe.

Previous cleanings have revealed modern debris, including traffic cones, shopping trolleys and even a moped.

The steps, which were rediscovered in the 1800s, and the Great Bath's lead lining are more than 2,000 years old.

More than 1,000,000 people visit the baths each year.