This is OSGrid Ref SX99. A 100km2 area that captures most of the City of Exeter, UK. It was merged together from 40 or so separate scans, aligned to match satellite imagery from a separate source to provide point colours, oversampled areas were decimated to a more or less uniform 50cm interval, then moved to origin and saved as PLY with as X Y Z R G B binary. Then it was read into Unity with Point Cloud Importer by Keijiro Takahashi.
It's about 90M points, stored in 1.3GB.
Once the data is processed into a realtime format it can be used for civil engineering, urban design, environmental impact (flooding) visualisation.