The Nature Reserve Dimmuborgir, „The Dark Castles”, are among the most visited and admired spots on lake Myvatn.  It resembles a maze and people have to be careful not to loose their way, because prominent landmarks in the vicinity are not visible from the depression in the lava landscape.  It is rather a small area, only about 1 km in diameter.

About 2300 years ago a major eruption started, when a 12 km long volcanic fissure opened up a short distance away to the southeast.  During the eruption, the flowing lava met some kind of an obstruction in the Dimmuborgir area and a temporary lava lake was created.  Dimmuborgir are peculiar lava formations in the Younger Laxa Lava Field. A pool of molten lava, about 2 kilometres in diameter, was formed there during the fissure eruption of Ludentsborgir. This pool was drained when the lava exited towards Lake Myvatn, leaving behind high pillars of lava, which have taken on most bizarre forms. It is believed that these pillars were formed in the pool where steam percolated through the molten lava and cooled it. Horizontal lines, formed when the half-congealed lava crust of the pool gradually collapsed, are a frequent sight in the lava. The collapsing crust also coated the pillars with scoria, which can be seen in many places as a thin coating with vertical etchings.

Lava formations like Dimmuborgir have been found at the bottom of the ocean off the coast of Mexico but are not known to exist on dry land outside the Lake Myvatn region. The lava pillars at Hofdi (named Klasar and Stripar) are similar formations.

An earlier eruption, 3800 years ago, also altered the landscapes on the lake considerably. The eruptive fissures are side by side and the whole area offers great opportunities for short or long, light hikes.  Quite a few species of birds breed down there and the visitors are kindly asked not to disturb them during the breeding period and stay on the marked paths.  It is strictly forbidden to leave them and to climb the lava cliffs.
Painting: David Haraldsson.

The Dimmuborgir are also the home of the Icelandic Yule Tide Lads and their parents:
Old sources do not agree on their total number in and vary between the different parts of the country.  Some refer to 13 others to 9.  According to common practices nowadays, their number is 13.  They are the sons of the ogress Gryla and her subservient husband Leppaludi.  Badly behaved children were threatened with the ugly Gryla, and were told, she would come and take them away and cook them for dinner.  This large family keeps quiet until Christmas approaches.  Then the Yuletide lads start appearing, the first one 13 days before Christmas.  Their behaviour is very unusual and they are all dressed in old-fashioned clothing or rags and their names originate in the old society of farmers and country folks.  They do not wear the clean red and white attire of Santa Claus.

The first one to arrive in civilized areas is
SHEEP COT DOLT, who heads directly for the sheep cot to have fun with disturbing the sheep.  The second one to arrive is

GULLY GAWK, who rushes for the cowshed to try to get some milk. The third one to arrive is

STUMP, who is extremely attracted to the contents of the kitchens, and does not miss a chance to
snatch something to eat.  The forth one to arrive is

LADLE LICKER, who is very lean.  He concentrates on finding pots with something well tasting and
licks the ladles.  The fifth one to arrive is

POT CLEANER, who consumes the burnt layers of food from the pots and leaves them shining clean.
The sixth one to arrive is

FOOD BOWL LICKER, who always arrives late enough to get to the food rests left by the children and
finish the food from their bowls.  The seventh one to arrive is

DOOR SLAMMER, who hides in dark corners and waits for the opportunity to tease the people at the
farms and slams the doors during the night to wake everybody up.  The eighth one to arrive is

SKYR GOBBLER, who thinks of nothing but gourmet food and steals skyr from the larders, whenever he gets the opportunity.  The ninth one to arrive is

SAUSAGE PICKER, who raids the larders, because of his constant hunger, and prefers the well-tasting sausages.  The tenth one to arrive is

PEEPING TOM, who is extremely curious.  He makes faces at the windows to scare the children, who run and hide, but the grown ups only laugh. The eleventh one to arrive is

DOOR SNIFFER, who uses his sensitive nose to find all kinds of things, especially food, standing in doorways of houses.  The twelfth one to arrive is

MEAT HOOK, who likes smoked lamb very much, spares no effort to hook a leg of lamb from the stove through the chimney.  The last one to arrive is

CANDLE BEGGAR, who fancies candle lights and never gets enough candles for himself although he snatches quite a few from the children.

Immediately after they have all gathered in the inhabited areas and entertained people, they start back to their parents one by one until the 6^th of January, when the Icelanders celebrate with bonfires and fireworks the end of Christmas and the time of year, when the elves move house and travel about in their colourful attire on horseback.  New year’s eve is also celebrated with much ado, large bonfires and hours of fireworks until the wee hours of the morning.