The historical Kuninkaanlähde (Royal Spring) and the old watermill are located in the village of Kankaanpää in Köyliö. Kuninkaanlähde is one of the largest springs in Finland, and it received its name after the visit of King Gustav III of Sweden in 1775.
From Säkylänjärvi to Kuninkaanlähde the spring flows along the stream Kuninkaanlähteenoja into Lake Köyliönjärvi. On Kuninkaanlähteenoja there are two water mills, one being Martin Vesimylly, which has been preserved and restored in the modern era.
Kuninkaanlähteentie 425, Köyliö