The secret water gates are located north of the Sofia bell tower in the Kremlin wall, in one of its lowest sections. This part of the ancient fortress remains mysterious and little studied. The unusual limestone masonry above the gates on the outside of the Kremlin suggests an earlier construction than the late 15th century. A.V. Vorobyov and S.N. Orlov proposed that there might have been a thirteenth tower here, but N.N. Kuzymina and L.A. Filippova disagree. Written sources from the 16th and 17th centuries indicate the presence of only water gates, and archaeological excavations conducted by S.V. Troyanovsky in 1995 found no traces of a tower.

The secret gates consist of an arched opening 430 cm wide with two side projections. The masonry above the gates on the river side is made of gray and brown limestone and is limited by a straight line. Studies in 1994 showed that the roadway of the gates, covered by arches and a vault, was built in the late 19th to early 20th century. Above the gates is a spacious vaulted chamber measuring 7x3 m, which was uncovered after the collapse of the western part of the wall in 1911 but was then bricked up. In 1994, another vaulted chamber measuring 3.6 x 4 m was discovered between the gates and the bell tower.

Comparing the building materials and masonry techniques shows that both chambers and the ancient part of the bell tower from 1439 belong to the same construction period, suggesting an earlier construction of part of the fortress wall with the gates than the late 15th century.

Currently, neither chamber has window or door openings, although they existed in the mid-18th century. V.S. Peredolsky saw them in the late 19th century, before the collapse of the western part of the wall. The purpose of these chambers is unknown. A.L. Mongait, who only knew about the upper chamber, suggested that the brother-in-law of the Crimean Khan was imprisoned there in 1551. It is possible that the chambers were used as guard rooms for the shooters, and the lower chamber originally housed a secret well.

In 1638, a wooden fortress with two quadrangular towers was built near the water gates and the secret. In 1660, the settlement was restored "according to the old layout" around the well, which was covered with "plank with a tent and around the well a railing." It is possible that after this, the well inside the stone secret ceased to exist. In the 17th century, a guard of five men stood in the towers of the Secret settlement, emphasizing the importance of these gates for the Detinets.

Previously, a procession passed through the water gates to the Volkhov River for the blessing of the Jordan water.