The mountain has a height of 626 m.[1] The volcano dates from the Mid-Holocene, is - following B. Hróarsson - about 6,000 years old, slightly younger than the Selvogsheiði, another shield volcano on Reykjanes peninsula,[1] whereas Sinton defines its age as “finiglacial”, i.e., from the beginning of Holocene.

[1] The lava flows from Heiðin há went in all directions on Hellisheiði: They covered the highland up to the Bláfjöll and up to the tuya Geitafell [ˈceiːtaˌfɛtl̥] in eastern direction, and enclosed the older shield volcano Selvogsheiði [ˈsɛlˌvɔksˌheiːðɪ] as well as the mountain Urðarfell [ˈʏrðarˌfɛtl̥].

[3] The slopes of the shield volcano are cut by small canyons, including Strandagjá [ˈstrantaˌcauː], Hrossagjá [ˈr̥ɔsːaˌcauː], Réttargjá [ˈrjɛhtarˌcauː] and Götugjá [ˈkœːtʏˌcauː].

[1] The trail leads from the farms near the Selvogur bay (Árnessýsla) on the south coast of Reykjanes up to Hafnarfjörður in the vicinity of Reykjavík.

[4][5] This old trail, Selvogsgata, traverses a big part of the slopes of the shield volcano Heiðin há.

It took the farmers about 14 hours to get with their herd from Selvogur to the market town, with snowfall parts of the way.

[4] The trail begins near Strandarkirkja, a church on the southern coast of Reykjanes west of Þorlákshöfn.