VIIKINMÄKI WASTE WATER TREATMENT PLANT IN HELSINKI
Underground waste water treatment is one of the best rock engineering products. 
Modern, highly efficient treatment plants can be located under urban centres, 
saving valuable building land and eliminating the malodorous drawback of sewage 
treatment in surface plants.
Viikinmäki waste water treatment plant in Helsinki was built under a future residential area. 
The 1,000,000 m3 rock cavern was completed in 1994, since when the plant has 
been treating the waste water effluent of about 700,000 local residents and industry.