Smilsutornis, or the Sand Tower, was one of 25 towers that were part of the Swedish defensive wall surrounding the city. The tower defended the city from the Swedes and later the Russians and still has cannonballs lodged in its 10' thick walls to prove it. It was used to store gun powder in the 17th century, earning it the name Pulvertornisthe (Powder Tower). It is now the location of the Latvian War Museum.