https://www.bbc.com/news/world-europe-62717599

The discovery of thousands of undeclared private swimming pools in France has provided an unexpected windfall for French tax authorities.

Following an experiment using artificial intelligence (AI), more than 20,000 hidden pools were discovered.

They have amassed some €10m (£8.5m) in revenue, French media is reporting.

Pools can lead to higher property taxes because they boost property value, and must be declared under French law.