At the entrance to the Glamočko Polje, the Vrba stream springs forth in the village of the same name. It is considered a wonder, not of nature, but of spatial location, as it flows from the lower to the upper part of the Field.
However, Vrba is also a kind of natural phenomenon because the waters of this small stream divide into three branches: east, north, and west.
One part of the resurgence appears in Ključ and flows into the upper course of the Sana River, the second leads to the Pliva River in Jajce, and the third resurgence appears in the Sinjsko Polje, from where it flows towards the Adriatic Sea.