Zadar

In Zadar, there is a Sea Organ: organ pipes that are filled with seawater and produce sounds. Most of the time, it sounds relatively consistent, but when the waves of a passing ship enter the organ, it startles you (at least me) with loud, high-pitched tones.

Near the organ, there is a large blue circle on the ground. When it gets dark, moving lights can be seen on it. In a line next to the circle, there are other circles of different sizes.

This is the model of the solar system. The large circle represents the Sun, and the lights are likely solar storms or something similar. The names of the planets are written on the edges of the smaller circles.