Vienna's location on the Danube made it a travel hub during the seventeenth century. However, river ships brought plague-bearing rats. In addition, the city did not have an effective way of disposing of garbage, which exacerbated the situation. People did not understand that plague came from fleas on these rats. They thought it was a punishment from God, so they tried to bribe God with ornate monuments such as this one, which was designed to thank God.