The elevation of the megalithic sites in Bulgaria tells us that they were built at a time when water levels were much higher than today. All megalithic sites in Bulgaria are situated at 250 metres elevation or above. There are no megalithic sites in the lowlands of the Thracian and Danube plains.
The location of the megalithic sites matches the elevation of the mountain ranges of Bulgaria: Central Balkan, Rhodope, Middle Mountain. These are old mountain ranges. The Middle Mountain that hosts so many megalithic sites has an elevation between 350m and 600-800m. And megalithic sites in the North Central Balkan are located at an elevation that ranges between 600m to 1200m. There are no megalithic sites in the newer mountain ranges of the Rila and Pirin.
The lack of megalithic sites in the lowlands and in the new mountain ranges helps us date the construction of the pyramids of Bulgaria. It matches the middle period of the Alpine orogeny during the Middle Miocene.
The elevation tells us about the world of the pyramid builders. They probably lived in a water world were sea levels were much higher and there were recurrent tidal waves and mega tsunamis.