In the XVI century, Moscow is starting to strengthen their defensive positions. Around the capital city appears a number of castles, among which the Holy Trinity Monastery. Wall monastery was intended to defend the approaches to Moscow from the north-east side.

In 1540, construction began on a powerful stone fortress. Ivan the Terrible himself monitor progress. He singled out for this purpose huge money in those days. An order was issued to use the right amount of brick and mortar, as well as all that is needed. To build the wall the king freed the peasants from all sorts of taxes and duties, even in difficult times. Trinity-Sergius Lavra for ten years turned into a powerful defense of the Moscow principality.

In the years 1608-1610 served as a nice fortress during the siege of Hetman Sapieha and Lisowski. Year, three months and twenty days the monks defended their positions without the help of the army. 15000th enemy troops were at the walls of the monastery, tried to storm the castle, but the monks and peasants of the district, even defended the bombing of 60 guns. Walls of red brick in the construction of deliberately bleached to blows when guns could not see the holes. When the Poles began to conduct saps Nikon Shilov and slots - the defenders of the monastery - got into one of those manholes and blew it with me. The superior forces of the Polish army retreated, and the courage and the will of the defenders of the Holy Land inspired to liberate Moscow. After this siege, in the middle of the XVII century walls we have built and expanded.

Now the length of the fortress walls is about 1,200 meters .  The wall thickness reaches in some places up to 10 meters and the height varies from 7 to 15 meters .  Four towers at the corners of the wrong quadrangle and seven were on the walls for extra protection .  Caliche is not intended for the defense, and served as a design entry for pilgrims .  Its name says exactly that .  Over the Holy Gate - the main entrance to the monastery - is Red Tower .  In 1856, over the gate there was a portal with beautiful moldings and the image of the Holy Trinity of the Ural stone, and the tower itself has acquired a semi-circular dome with a bulbous head .  In the north-east corner of the fortress is made more precise Tower (formerly Zhitnichnaya), which acquired its current name due to the white-stone carved duck decorating the top .  She and two other corner towers have a polyhedral shape, and the tower over the water gate Contrary made more precise "Foursquare" .  Scientists believe that all the corner towers are already in the XVI century were underground storeys .  The most beautiful believe bartending tower standing on the western wall on a steep slope .  The height of its almost 20 m .  It is the largest of the towers pryaselnyh .  Only it has four stages, rather than three, as in the other .  Through ten-meter drop of land inside and outside of the tower and a wide gate, misleading, it served as a prison cell for the enemy and a convenient outlet for monks .  Bloc sees tower guests and residents of Sergiyev Posad, being on the observation deck Blinnaya Mountains . 

The walls between the towers have three tiers of combat. Lower for 'plantar battlefield "and it is open from the monastery arcade. Above it - a battle in the middle vaulted galleries with battlements and an open upper storey with serrated edge. Gallery allowed to go around the monastery on the wall. It gave maneuverability in combat. Inventory in 1641 states that the monastery held a 90 guns on the walls, and 20 were in reserve.

The moat surrounding the monastery served as an additional barrier to the enemy. In order to increase the inaccessibility of the fortress walls were constructed dam, and on the south side, you can admire the huge pond cellarer, arranged in 1552 and decorating Sergiev Posad until now.