Before the merger, Gadmen had a total area of 116.6 km² (45.0 sq mi).
 As of 2012, a total of 9.62 km² (3.71 sq mi) or 8.3% is used for agricultural purposes, while 19.48 km² (7.52 sq mi) or 16.7% is forested.
  The rest of the municipality is 0.75 km² (0.29 sq mi) or 0.6% is settled (buildings or roads), 1.52 km² (0.59 sq mi) or 1.3% is either rivers or lakes and 85.19 km² (32.89 sq mi) or 73.1% is unproductive land.

During the same year, housing and buildings made up 0.1% and transportation infrastructure made up 0.4%.
 All of the forested land area is covered with heavy forests.
 Of the agricultural land, 1.7% is pasturage and 6.5% is used for alpine pastures.
 Of the water in the municipality, 0.4% is in lakes and 0.9% is in rivers and streams.
 Of the unproductive areas, 13.3% is unproductive vegetation, 33.0% is too rocky for vegetation and 26.8% of the land is covered by glaciers.

On 31 December 2009, Amtsbezirk Oberhasli, the municipality's former district, was dissolved.
 On the following day, 1 January 2010, it joined the newly created Verwaltungskreis Interlaken-Oberhasli.

Gadmen lies in the Bernese Oberland, and the Susten Pass lies on the eastern border of the municipality.
 It lies in the Gadmer watershed.
 The municipal borders stretch from the valley floor, with an elevation of 850–1,250 m (2,790–4,100 ft), up to the nearby mountain peaks at about 3,500 m (11,500 ft).
 It is located on the border of the Canton of Bern with the Cantons of Obwalden, Nidwalden, Uri and Valais.
 The neighboring municipalities are Engelberg, Wassen, Göschenen, Guttannen, Innertkirchen and Kerns.

There are three glaciers in Gadmen, the Stein Glacier, the Trift Glacier and the Wenden Glacier.
Beneath the Stein Glacier is Lake Stein.
The most famous mountain in Gadmen is the Titlis.
Before the merger, Gadmen had a total area of 116.6 km² (45.0 sq mi).  As of 2012, a total of 9.62 km² (3.71 sq mi) or 8.3% is used for agricultural purposes, while 19.48 km² (7.52 sq mi) or 16.7% is forested.   The rest of the municipality is 0.75 km² (0.29 sq mi) or 0.6% is settled (buildings or roads), 1.52 km² (0.59 sq mi) or 1.3% is either rivers or lakes and 85.19 km² (32.89 sq mi) or 73.1% is unproductive land.
During the same year, housing and buildings made up 0.1% and transportation infrastructure made up 0.4%.  All of the forested land area is covered with heavy forests.  Of the agricultural land, 1.7% is pasturage and 6.5% is used for alpine pastures.  Of the water in the municipality, 0.4% is in lakes and 0.9% is in rivers and streams.  Of the unproductive areas, 13.3% is unproductive vegetation, 33.0% is too rocky for vegetation and 26.8% of the land is covered by glaciers.
On 31 December 2009, Amtsbezirk Oberhasli, the municipality's former district, was dissolved.  On the following day, 1 January 2010, it joined the newly created Verwaltungskreis Interlaken-Oberhasli.
Gadmen lies in the Bernese Oberland, and the Susten Pass lies on the eastern border of the municipality.  It lies in the Gadmer watershed.  The municipal borders stretch from the valley floor, with an elevation of 850–1,250 m (2,790–4,100 ft), up to the nearby mountain peaks at about 3,500 m (11,500 ft).  It is located on the border of the Canton of Bern with the Cantons of Obwalden, Nidwalden, Uri and Valais.  The neighboring municipalities are Engelberg, Wassen, Göschenen, Guttannen, Innertkirchen and Kerns.
There are three glaciers in Gadmen, the Stein Glacier, the Trift Glacier and the Wenden Glacier. Beneath the Stein Glacier is Lake Stein. The most famous mountain in Gadmen is the Titlis.
Gadmen