The area of Koigi swamps is 3980 ha and it is the biggest peer in the whole Western Estonia archipelago. Swamp has diversified and interesting nature where live several nature rarities. Defined are 35 species of plants. In the bog part there are four rudimentary lakes: Koigi, Pikk, Ümar and Naistejärv. This area is very important from bird population protection point of view.
Interesting to know: Naistejärv was believed to be created from the tears of women, including the wife of Suur Tõll Piret. Koigu lake was created according to old peoples believe in the place where Kareda and Koigi manor owners had fight and in the bottom of the lake it is believed there is the whole manor.