The largest spring in Iceland is Deildartunguhver – constantly boiling pool of geysers and spouters. This might be the most powerful thermal spring in the world. And… one more record: here starts the longest district heating system in the world!

Geysers and hot springs

Deildartunguhver is named after Deildartunga – nearby farm which has been mentioned already in the Icelandic medieval sources. This was valuable agricultural land long before the use of geothermal energy started. The fate of the legendary Snorri Sturluson (1179-1241) is linked to this site as well.

Deildartunguhver is located in Reykholt geothermal area. This area of thermal water includes one more unique landmark: the nearby Árhver geysers in the middle of a river.

Springs emanate at the foot of Hverahóll hill and have at least nine vents. The temperature of the water at the surface here is 95 – 97 °C. A little deeper it is above the boiling point.

Steam around Deildartunguhver
Steam around Deildartunguhver. / Reykholt, Wikimedia Commons / CC BY-SA 3.0

Some of the spring vents behave as water spouters and even geysers. The most active ones can erupt up to 3 m high. In 1810 the geysers were taller – up to 4 m – as described by Scottish geologist Sir George S. Mackenzie.

Deildartunguhver almost continuously is shrouded in dense steam. Thus it is hard to find a moment to take a clear picture with the springs.

District heating system

In the 1970ies, during the oil crisis, a dire need for cheaper energy arose. As a result, a very ambitious project was realized around 1979: there was built a district heating system between Deildartunguhver and the coastal towns – Borgarnes and Akranes. The pipe to Akranes is 64 km long. Water at the end of this pipe still is very hot: 78 – 80 °C.

Later there were found other sources of geothermal energy nearer to the towns – but too late, the system was built and functional.

Here the water from Deildartunguhver starts a path in world's longest district heating system
Here the water from Deildartunguhver starts a path in world’s longest district heating system. / bowlingbal, Wikimedia Commons / CC BY-SA 3.0

Thus, the visitors of the site can see how twisted can be the compromise between nature conservation and development. Deildartunguhver is a protected monument of nature. But, as the water appears above the ground and flows for some meters, nature conservation ends: water reaches a system of concrete gutters and disappears in pipes.

The only endemic plant in Iceland

These few meters of “freedom” though are very important. Around the hot springs grows a unique plant, which is found only here: the fern Struthiopteris fallax. In 2019 this small plant (2-5 cm long leaves) was confirmed to be a separate species. This is the only unique species of plants in Iceland.

Struthiopteris fallax - fer which grows only at Deildartunguhver
Struthiopteris fallax – fern which grows only at Deildartunguhver. / Ragnhild&Neil Crawford, Wikimedia Commons / CC BY-SA 2.0

One more important find is thale cress (Arabidopsis thaliana) – the only find of this plant in Iceland.

Deildartunguhver is included in the following article:

Geysers of Iceland
Geysers of Iceland on the map
Geysers of Iceland on the map / Wondermondo / public domain

Some of the world’s most popular geysers are located in Iceland. But few know about ALL active geysers in Iceland.

This article lists all the known active geysers in Iceland – some 20 – 29 of them. Here are listed also some 38 other places where geysers have existed in the past or features, which are similar to geysers but are not genuine geysers.


  1. Dirk Niemann, Deildartunga / Reykholt, Volcanic Springs. Accessed on June 2, 2019.
  2. Sonia Molino, Jose M. Gabriel y Galán, Pawel Wasowicz, Pablo de la Fuente, Emily B. Sessa, The Struthiopteris spicant (Blechnaceae, Polypodiopsida) complex in Western Europe, with proposals for taxonomic and nomenclatural changes, Plant Systematics and Evolution (2019) 305:255–268. Accessed on June 3, 2019.
Deildartunguhver on the map
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Location, GPS coordinates: 64.6636 N 21.4107 W
Categories: Thermal springs, Geysers, Ecosystems
Values: Geology, Visual
Rating: 3 out of 10 stars
Where is located? Europe, Iceland, Western Region (Vesturland), some 7 km west from Reykholt, at Krauma Spa, in Reykholtsdalur valley
Alternate names: Tunguhver (in older sources)
Height: Up to 3 m
Average discharge: 180 l/s

Video of Deildartunguhver

For 91 Days Travel Blog, September 2013

Landmarks of Iceland

Gullfoss, Iceland
Gullfoss / WoSie, Wikimedia Commons / CC-BY-2.5.
Iceland is very rich with peculiar natural landmarks and the island contains also interesting cultural landmarks. The highlights of Iceland are the magnificent waterfalls as well as geysers and other geothermal features.


Geysir and Strokkur erupting simultaneously, June 1984
Geysir and Strokkur erupting simultaneously, June 1984 / Roger Goodman, Flickr.CC BY-SA 2.0.
Hasty hydrogeologist would say: geysers are thermodynamically and hydrodynamically unstable hot springs. “Normal” people would say – geysers are hot springs which at more or less regular intervals shoot up a fountain of boiling water and steam. Sometimes these fountains are even 100 m tall… or even 450 m!

Recommended books

Iceland Travel Guide

Iceland Travel Guide Introduction This book includes all the necessary links for an easy journey to your Icelandic adventure. To make your Iceland travel more entertaining and full of all of the things that you want, you’ll see a step-by-step route around the entire country, indicating the distance in miles, accommodations, recreation, entertainment, shopping and much more. This Iceland travel guide will be the perfect companion to see all of the hottest spots, like Blue Lagoon, Iceland and other must-sees.

The Glorious Geology of Iceland’s Golden Circle

This is the first book describing the glorious geology of Iceland’s Golden Circle and four additional excursions:(1) the beautiful valleys and mountains of the fjord of Hvalfjördur, (2) the unique landscape and geothermal fields of the Hengill Volcano, (3) the explosion craters, volcanic fissures, and lava fields of the Reykjanes Peninsula, and (4) the volcanoes (Hekla, Eyjafjallajökull, Katla), waterfalls, sandur plains, and rock columns of South Iceland. The Golden Circle offers a unique opportunity to observe and understand many of our planet’s forces in action.

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