As a kid I found a bifurcation island in northern Sweden, that may be bigger than Gotland, the conventionally biggest island in Sweden.

It's formed by the Tärendö River which flows from the Torne river to Kalix river.

It's supposedly the second biggest bifurcation in the world: https://en.wikipedia.org/wiki/T%C3%A4rend%C3%B6_River

This is the best image I found: https://www.smhi.se/polopoly_fs/1.30940.1490013619!/image/%C...