Long Lake is an artificial lake above Arindell, impounded by a series of dams, which feeds the Mourn River. The dam was contructed in Eieber's time to ensure a stable water source for the city, but was replaced several times during the Golden Age.
The first dam impounding Long Lake was an earthworks construction of mud brick. It was a mammoth structure for its time, but breached in the early Golden Age and caused severe damage downstream, even in Arindell proper. Initial talks of reconstructing it were fast-tracked when unusually heavy rains caused flooding on the Mourn. A strong, simple dam of cut stone was added for flood control.
By the end of the Golden Age, the city's water demands were serious, and the simple flood control dam was not impounding a large enough reservoir. The Alliance government contracted the Gudersnipe Foundation to construct 'an edifice that could last all the days of the Alliance'.
The Foundation delivered, building the massive Lieber Dam, a concrete arch structure a thousand feet high and over two thousand long. It created a considerably larger lake than the Alliance had originally called for, enough to feed an extensive canal network connecting the Stormreaver Valley to the Agras Plains and hold water to supply the city for over a century.
In front of Lieber Dam, a second, even larger edifice was constructed, this time an enormous gravity dam, created as a precaution against overtopping. The two structures together, the Foundation assured, were effectively an artificial mountain.
In addition to storing water and preventing floods, Lieber Dam produces hydroelectricity, to meet about 70% of Arindell's needs. The area around the lake is far enough from the city to be outside the protective shield, making it an ideal location for an air base. The lake is still situated high on the slopes of High Mountain and surrounded by ridges and subsidiary peaks. Both the Alliance and the Crimson Blade base fighter jets here, and small aircraft service the surrounding regions. However, the location is too challenging to admit commercial passenger aircraft.