Mystery of Hagia Sophia - the same things found in Sri Lanka and Turkey. What are these – sarcophagus or anabiosis bath tubs?

Hagia Sophia (Holy Wisdom, the unique 1500 years old Orthodox temple),
served as Eastern Orthodox cathedral and seat of the Patriarchate of Constantinople

Recently I've been to Istanbul (Turkey) and visited Hagia Sophia temple where I saw the same things as in Mihintale, Polonnaruwa and Anuradhapura (Sri Lanka) before – very special "bath tubs" or "sarcophagus" (on the photos below) which look completely the same.

You can read about Sri Lankan "sarcophagus" here: Mihintale, Sigiriya and Yapahuwa: mysterious triangle of sacral objects, memory of whose went through the Millenniums. Masonic symbols before the Buddhist era. Chapter 4 of a Detailed Photo Essay on Sigiriya.

The mysterious stone "sarcophagus", carved by shape of the human body 

silhouette, located on the territory of Hagia Sophia (Holy Wisdom, 

the unique ancient Orthodox church), Istanbul, Turkey.