The average Dolmen is made of 9 1.5 to 5 tons stones. in most cases there are 4 stones which serve as the floor upon which the structure stands. 4 other stones make the walls, one of these always has that round hole. one big stone makes the roof.
A "big" Dolmen would be 1.8 meters high at it's highest point, (usually the "front" where the hole is).
The 4 stones making the walls are rounded on the outside. they "sit" in a slot made in the floor stones and the top stone. in the same way, the front and back stone sit in a slot made in the 2 side wall stones. these slots show patterns in some of the cases and some beleve this is evidence of machinery.
It seems to me that this chamber was deigned to be sealed, as well as to last long.
The dolmens have corks, which go into the round holes. i fist stumbled upon them in the museum in Gelindzhik. (more pictures are in the gallery to the right.
It is finding a cork like this just beside a more or less complete dolmen, that convinced me they really are corks. In my opinion, a complete, undisturbed dolmen with its cork might even be waterproof, it would protect from rain as Well as it could hold water. More about the dolmen's functionality, purpose, and who made them can be found on The Theories page.
I am not a trained geologist but it seems that the massive stones which make the dolmens are local. I believe they were dug out at the very spot the dolmens stand. More about why this seems likely can be found on the Topography & Geology. page. The stone is soft like sandstone and is made of thin layers. I assume it would be lighter than granite or basalt. It is relatively easy to break it in straight lines. Drilling a symmetrical round hole through a 30-40 centimeter block of stone is feasible, but would take some skill. Managing, positioning and fitting one ton stones isn't an easy task. Positioning the stones and mounting the structure using bronze age methods and knowledge would be a huge effort.
that there are dozens of dolmens just around Gelindzhik, Russia, imply one of the tow:
there is a really good reason to build the dolmens the way they are built.
the way they are built is the cost effective way, the easy way to do it.
Some features and finds are not consistent across all sites and only appear in one or two sites. Some dolmens were "restored" and enhanced for tourist purposes. These enhancements include cutting doors into the front stone or adding a balcony and maybe some decorations. Site by site exploration can be found on the Explore by Site page.
I found two dolmens which are made of a single stone. The floor and the four walls are carved out of a single stone blocks and I imagine a top stone would cover that to make a roof.