Built in the 13th century. The Great Round Tower or Bergfried is the main constituent part of the castle buildings therefore is it called the Main Tower. It was designed for observation of surroundings and defence of fortification. It was used as a last shelter during the attack. To provide the inaccessibility of the tower, the entrance in the bergfried was located 9,5 m above the ground at the level of the 3rd floor. One could get in the tower by using wooden stairs, in case of danger, easily pulling them down or burning. Bergfried is one of the first castle buildings. The top of the tower is formed by conical cupola, but the walls – by breastwork with tablings and loopholes. For observation of the surroundings and on the purpose of defence only top floor was used. The lowest floors were not used on this purpose, because the narrow windows were planned for lighting the rooms. In the period of peace the tower was not inhabited. On the eastern side of the tower there was located a crucifix, covered on the top by arch. It was a place for open-air religious ceremonies.
Walls of the tower were revetted with long bricks 9x15x33,5 cm. The thickness of walls in the most endangered northern part was 3,7 m, in the southern part – approximately 2,9 m. The tower has 5 floors, the 3rd and the 5th floors are vaulted. The hight of the masonry reaches up to 29,20 m, the hight up to the spire – 38,25 m. The outside diameter of the tower – 13,40 m, but inner diameter – 6,80 m.
Until the beginning of the 20th century the remains of the tower had preserved at the level of 27 metres. At that time the upper part of the tower and decks had collapsed. In 1936, the remains of the Main Tower were restored and on the upper part of the tower there was built the observation platform. A door opening was built instead of the former breach for visitors` convenience. From 1953 until 1959 under the guidance of the architect Kārlis Vikmanis there was carried out restoration of the Main Tower. The collapsed upper part of the tower was renovated and capped by a steep tented roof covered with tiles. In the upper part of the masonry there was made a frieze with the motif of the Romanaesque arcade. Several mezzanine floors were constructed in the tower. The observation platform was arranged on the upper floor. In order to make the admittance into tower easy, the door opening was renovated and built the inner staircase.
From the observation platform of the Main Tower (approximately 120 m above sea level) unveils a picturesque landscape to the ancient valley of the River Gauja, castle yard and the territory of Turaida Museum Reserve.
The exhibition, installed in the Main Tower, informs about the building history of the tower and restoration.