The Armenian Highlands are pierced with countless ancient cave dwellings that date back to the earliest pages of human settlement. Investigations of the Areni cave complex in Armenia provided the archaeologists with such phenomenal finds as a straw skirt (6,000 years old), the oldest leather shoe (5,500 years old), the oldest winemaking facility (6,100 years old), traces of early animal domestication, and even a well-preserved human brain.
There are caves of almost any kind in Armenia, ranging from man-made caves to exceptionally rare caves of hydrothermal origin, which form when lava from the inner core of the earth mixes with hot springs. However, man-made caves are no less remarkable. The architecturally sophisticated monastery complexes with villages carved out in the rock are abundantly spread throughout the Armenian Highlands. Ancient Armenians utilized caves as fortresses, temples, storage facilities, dwellings, as well as sheds for their animals. Thanks to the minimal air flow in the caves, their interior was warm in winter and cool in summer.
Ancient Armenian cave dwellings have been well-known to ancient chroniclers. During his journey in Armenia, Xenophon described an Armenian cave-village as follows:
“Their houses were under ground, the entrance like the mouth of a well, but spacious below; there were passages dug into them for the cattle, but the people descended by ladders. In the houses were goats, sheep, cows, and fowls, with their young; all the cattle were kept on fodder within the walls. There was also wheat, barley, leguminous vegetables, and barley-wine, in large bowls.” 
Utilizing caves as a place for dwelling has been common during the entire Armenian history. In fact, caves have been used as housing by the Armenians up until the 1960s. Today, the caves situated in a close vicinity to modern villages Tegh and Khdzoresk in Syunik Province, Armenia, are used as cellars and cowsheds.
In his “Armenia” (1842), Mr. Curzon in-depth described the construction of cave dwellings in Armenia:
“First, a site is selected on the side of a gently sloping hill. Then a space as large as the proposed house is excavated. This is divided off into quarters for the stock and rooms for the family by walls and rows of wooden columns, eight or nine feet high. Over these large branches of trees are laid, with a thick layer of smaller branches and twigs on top. Then a large part of the earth taken out in the excavation is spread above, and a layer of turf completes the roof. The houses are now entered through door-ways on the lower side, which is built up four or five feet above the grade of the slope.” 
Sir Austen Henry Layard recounts his discoveries in Asia Minor and the Middle East in his book “Discoveries among the ruins of Nineveh and Babylon: with travels in Armenia, Kurdistan, and the desert…” (1859). In one of the passages, Layard describes several ancient Armenian cities he had encountered during his journey, among many others recalling Khelath (Ahlat):
“The lofty perpendicular rocks rising on both sides are literally honeycombed with entrances to artificial caves, ancient tombs, or dwelling-places. On a high isolated mass of sandstone stand the walls and towers of a castle, the remains of the ancient city of Khelath, celebrated in Armenian history, and one of the seats of Armenian power. I ascended to the crumbling ruins, and examined the excavations in the rocks. The latter are now used as habitations, and as stables for herds and flocks.”
The cave Monastery of Geghard is another remarkable site located in Kotayk Province, Armenia. It is partially carved out in the adjacent mountain and is surrounded by cliffs. The monastery is inscribed in the UNESCO World Heritage Site List. Geghard Monastery was founded by Gregory Illuminator in the 4th century at the site a sacred pagan cave holding one of the purest water springs in Armenia. Apart from that, Geghard Monastery houses a number of cave churches and tombs.
360-degree view of Geghard Monastery.
Some cave houses situated throughout the Armenian Highlands feature a stone door. The Speleological Center of Armenia over the decades has discovered over 160 man-made structures carved into rocks, as well as cave dwellings in the territory between Araler and Aragats and between Talin and Ashtarak. These are the caves distinguished with stone doors. They also have a cave-hall and a secret entrance in the form of a tunnel with differing masonry. Those had been mainly used as storage facilities for the food of small communities. It seems that only a few trusted people had access to the food reserves. The end of the tunnels featured the unusual stone doors.
In fact, those stone doors were a key feature of those caves. Hidden tunnels were always closed off by stone doors, which had pegs near their top that fit into holes specially carved into the doorframes. Remarkably, both the doors and their frames were well-finished: they can be opened and closed even today. It is unknown when those doors have been built, but they certainly had no practical use by the 18th century. Ancient Armenian chroniclers described them as amazing, unusual structures presented to humans by mythical giants.
According to the Armenian Speleological Center, caves with such stone doors are frequently found in Aragatsotn Province. Interestingly, there are no rock-carved churches in the region. Apart from that, the churches built between the 5th and the 16th centuries don’t have stone doors, which allowed researchers to conclude that the caves with secret tunnels were constructed in the pre-Christian times.
Saghmosavank, Khosrov & Goris/Kndzoresk caves: Interesting Triple of Armenia: Part 3