Only in recent years it has been possible to establish the key construction phases of Cēsis Castle, but detailed studies on individual parts of the site and their functions in relation to one another are ongoing. Today, it is the castle’s massive towers that leave the greatest impression. This is no coincidence! Towers often have another role - they embody and demonstrate a sense of power and authority. Architecture has always been the best tool for that. One of the best-known parts of Cēsis Castle - its South Tower - was inaccessible to the public for a long time, as its walls were in a bad state and posed a safety risk to visitors. In 2020, following years of conservation work, it opened again. This article introduces readers to the tower’s architecture and its construction history. It is based on the latest research carried out by experts from a range of fields. The dating of archaeological material allows us to conclude that the South Tower was built at the same time as the external walls of the adjacent ranges - in the second or third quarter of the 15th century. This builds on the existing information regarding the construction of artillery towers at castles in the territory of Latvia where Bauska Castle, built in the 1440s, is considered the first point of reference. The fact that the South Tower has no horizontal defence infrastructure at its lower level is also characteristic of earlier structures. According to the latest studies on the development of castles in Central Europe, such fortifications suitable for horizontal defence began to be built in the second half of the 15th century. Large, monumental cannon towers followed even later – in the late 15th century, and the 16th century. A study of the tower’s structural composition reveals that it was extensively rebuilt and renovated in the 1540s. It is likely that the south side of the tower, from the 2nd to 5th floors, was rebuilt at this time, resulting in the current shooting chambers, arcades, and vaults on the 2nd and 4th floors. The north side of the tower with its fireplaces and staircase dates back to the initial stage of construction. The tower’s facades were painted an earthy red, with some details highlighted in white. Fragments of the tower walls found during archaeological excavations, as well as the unused lead cannonballs retrieved from the moat, testify to a disaster after which the tower was not rebuilt. The tower walls could have collapsed after the intense shelling of the castle during the siege of 1577. Following the Livonian War, political and economic onditions, as well as changes in military architecture, were not conducive to the restoration of the castle’s imposing towers. The renovation of the tower in 1938 was carried out without completing thorough project documentation and architectural research. As a result, extensive and important information about the tower’s construction history was lost. This is particularly relevant to the structures on the 4th and 5th floors, as well as the fireplace area. Research of the South Tower confirms that determining exact dates when separate parts of the castle were built is difficult. However, combining different research disciplines leads to increasingly reliable results. The tower at the south corner of Cēsis Castle is the most beautiful of the castle’s towers and has a vividly decorative facade. Its dungeon is one-of-a-kind in the castles of Latvia. There are no other equally well-preserved shooting chambers in near-by castles with such an intricate design, layout, and authentic gun rests. The tower can therefore be considered an outstanding masterpiece of medieval military architecture in Latvia, built during the transition period from cold weapons to firearms, but modified at the time when military doctrine changed. When the South Tower was rebuilt in the 1540s, European military architecture was gradually shifting towards a horizontal defence style with ramparts and bastions. Livonian castles were modernised and rebuilt in line with the advancement of firearms, which correlates with the overall development of Europe’s fortifications. However, due to historical events, Cēsis Castle never witnessed such advances since it ceased to be of strategic significance.