Lake Vesijärvi has become world-famous for its fresh water restoration project. After urban development really took of here in the 50s, the lake rapidly became severely eutrophic due to household and industrial wastewater being fed into it. Since the 70s, Vesijärvi’s condition has improved significantly and Lahti has gained robust expertise in all things water, due to its large natural bodies of water and the persistent protection and restoration work carried out in co-operation with several organisations. Vesijärvi is the largest fresh water restoration project in Finland with the aim of reducing the excessive loading of the lake. The City of Lahti invests more than EUR 250,000 in the restoration of the lake every year. The region has become a pioneer in projects and research focusing on both surface and groundwater restoration methods, e.g. direct precipitation of phosphorus, oxidation, biomanipulation and draining. The current restoration work involves multiple methods, such as mapping pollution sources, eliminating wastewater sources from private dwellings, constructing retention ponds and wetlands, and biomanipulation (fishing roach, bream, and bleak, and stocking with predatory fish). The lake is also aerated near Lahti. There are many restoration methods for which Lahti has been among the pioneers, including direct precipitation of phosphorus, oxidation, biomanipulation and drainage of Lake Vesijärvi. Mapping pollution sources, eliminating wastewater sources from private dwellings, constructing retention ponds and wetlands, and biomanipulation are also important. Lahti promotes the efficient use of natural resources by putting the roach caught to good use by serving them as burgers. There is plenty of business in the water restoration industry, as well as an abundance of research underway in the area. The University of Helsinki and Ramboll Analytics have laboratories locally for water research and biotechnology experiments. The Lake Vesijärvi Foundation is a unique Finnish initiative to promote all efforts to improve the water quality. The Lake Vesijärvi Programme aims to maintain and improve the condition of the Lake Vesijärvi and other smaller water bodies in the region. Lahti Region Environmental Services is a part of the Lake Vesijärvi Programme and is responsible for the monitoring of the lakes and the largest ditches. Stormwater and wastewater treatment related issues are considered carefully when restoring or building new areas in Lahti. Challenges of the future when it comes to water protection include climate change, population growth and ever-denser city structures.