The High Fens (German: Hohes Venn; French: Hautes Fagnes; Dutch: Hoge Venen), which were declared a nature reserve in 1957, are an upland area, a plateau region in Liège Province, in the east of Belgium and adjoining parts of northwestern Germany, between the Ardennes and the Eifel highlands.

The provincial capital of Liège is to its west, the German border is to the east and the dark forested hills of the Ardennes surround the southern part.

[6] Signal de Botrange located in the Haute Fagnes is marked by a Telecom Tower erected over an older artificial, earthen mound with stone steps that was built to raise a small part of the broad plateau from 694 to 700 metres (2,277 to 2,297 ft).

Part of the High Fens reserve remains closed during the spring breeding season of the endangered black grouse (Tetrao tetrix).

[5][6] The Fagnes plateau intercepts clouds brought by the prevailing Atlantic winds, and this results in copious precipitation, with an average of 1,400 millimetres (55 in) of rain per year.

However, beneath the fragile composition of the overlying soils are rocky beds and clay that prevent infiltration of water and thus create the conditions for wetlands, marshes and bogs.

However, since the 17th century, peat cutting, drainage, inappropriate spruce plantations, infestation of the ground by the purple moor-grass, a herb, had caused problems for the ecology of the region.

The logo of the park is the seven-petalled flower of Chickweed-Wintergreen (Lysimachia europaea), not to be confused with other plants with similar names such as Chickweed (Cerastium spp.)

[13][14] Faunal species recorded are: the wild boar, roe deer, hen harrier, black grouse, wood mouse, grasshopper warbler, great grey shrike, meadow pipit, European stonechat and northern wheatear.

[14] Vertebrates, spiders and insects reported in the reserve are: orvet (Anguis fragilis), Odonata Orthoptera, Heteroptera Lepidoptera, diptera, crustaceans, myriapods and shellfish.

[15] As the habitat consists of bogs, fire is a major hazard during the drought period, when the Fens are closed except for a small area near Polleur [fr].

[5] Another notable monument is at Gèyeté (Gayetay) within the municipal boundary of Sart and Jalhay; it is in memory of eight American airmen who were the crews of two Douglas C-47 Skytrains from 50th Troop Carrier Squadron that collided in flight on 6 April 1945 due to fog.