The Tula Kremlin is a medieval Russian fortress built in the 16th century. The oldest building in the city and region, it was founded as a wooden fort by order of Tsar Vasily III, the father of Ivan the Terrible. Throughout its 500-year history, the Kremlin has never been captured because of the enemy’s attack and it was only once that it surrendered after a siege and a flood during the Peasant War.
The Tula Kremlin has a rectangular plan. At each corner there were towers protruding beyond the perimeter, so that it was convenient to provide flanking fire. There are entrance gates in the center of each wall, four in total: Odoyevskiye Gates in the south, Ivanovskiye Gates in the east, Pyatnitskiye Gates in the west and the Water Gate Tower in the north.
Restoration work in the mid-20th century revealed that the Kremlin walls and towers rest on a rubble foundation. Rubble is large rock fragments that are obtained during the extraction of limestone. There are oak piles or logs at the base of the Kremlin foundation.
The stone part of the foundation is almost three meters deep. Under the walls of the Nikitskaya and Spasskaya Towers, it can be twice as deep. A thorough study enabled the researchers to estimate the approximate number of piles under the walls of the old fortress — about 77,000 in total.
At the time of researching the layer under the Water Gate Tower, the piles were dark cherry in color. The structure of the wood is dense, hard, the even tops of the piles are slightly hewn. The piles had been placed at 15–25 centimeters from each other. The spaces between them had been filled with dense gray clay. In total, 49 rows of piles were found and about 190 pieces were removed in the area under the Water Gate Tower, which is about 13 meters long.
The foundation itself rests directly on the piles, enclosed on both sides in a shell of rubble blocks. On top they were covered by a layer of small rubble and crushed stone with lime mortar, 5 to 20 centimeters thick. This is quite a flimsy support for such a massive structure, erected on the bank of a river on unstable ground. Supposedly, the foundation had been built only under the tower gateway that was not too heavy, and the wall support had been much stronger.
