Exploration of the underground around Hotel Slavia on Solniční Street in 2002 uncovered a very interesting finding. The underground object of a medieval half-cylinder bastion was discovered by a probe made directly in front of the restaurant's summer garden at a depth of two metres below the pavement.

Initially, this finding did not differ from other discoveries. The inner space, with a backfill with remnants of rotten timbering, appeared to be a larger cellar.

After clearing out part of the rubble, however, it was clear that this was a much more valuable find. The stone wall, built in a round shape, suggested that other surprises would soon follow. After some more mining, an unspoiled part of the cellar revealed a medieval loophole: niches fitted with key gunshots. At that moment it was clear that the former fortified bastion had been discovered, at the height from where Brno’s ancestors defended the city. It was called the ‘Weise Pulwer Thurm’ (White Powder Tower). It was one of the few towers that were demolished in the last phase of the destruction of the walls and formed the corner of the northern and western lines of the medieval fortress belt. As its name suggests, it served as a gunpowder depot in addition to its strategic functions. Using towers to store this dangerous but strategically important material was common practice and a logical safety measure.

Accidental explosions, when there were no lightning conductors and the buildings were lit by open flames, were not unusual. One example is the explosion of seventy barrels of gunpowder stored in the Veselé brány (Merry Gate) tower. The explosion that occurred in 1580, which damaged many of the surrounding houses and literally tore the gate tower, was caused by lightning.