Task: Text Simplification
Input (English): In classical antiquity , Illyria ( ; , " Illyri ́ a " or , " Illyri ́ s " ; , see also : " Illyricum " ) was a region in the western part of the Balkan Peninsula inhabited by numerous tribes of people collectively known as the Illyrians .
Output (English): Illyria was an ancient region in the western part of today 's Balkan Peninsula .