The famous Maria Theresa Square in Vienna is home to four fountains, of which one include a mermaid.
The fountains are each at the center of one of the four rectangular garden areas that define the square.
This fountain depicts a Triton portrayed as an elderly man (with feet) on a conch shell being offered a strand of pearls by a twin-tailed mermaid. Created in Carrara marble by Austrian sculptor Anton Schmidgruber, it was unveiled in 1894.
All four fountains are referred to as Triton and Naiad fountains. In this fountain the female figure is the naiad (mermaid), whereas in the other three fountains the male figures are tritons (mermen with tails) and the female figures have human feet.
More details on the page for these fountains.