Complex sentence: The exact date of the founding of Burgio is not known, however it is known that it already existed in the 14th century, when the inhabitants of the nearby Scirtea joined those of Burgio.
Split into simpler sentences: The exact date of the founding of Burgio is not known. However, it is known that it already existed in the 14th century, when the inhabitants of the nearby Scirtea joined those of Burgio.