Unusual arch in village of Gojsalići, Croatia

I found this unusual, non simetric arch in small village Gojsalići. You might say it's done by amateur, but this arch is standing for several hundred years and reason is why is asimetric is probably the builder found two big pieces of stone that he has to adjust for the arch. And he has done it with great skill. Also, take a notice at the size of the stones below right side of the arch. Many houses and walls in this village and in the area around are built by megalithic blocks, some of them whighin more than 4 tons and matching perfectly.