source: As the largest sub-region in Mesoamerica, it encompassed a vast and varied landscape, from the mountainous regions of the Sierra Madre to the semi-arid plains of northern Yucatán.
target: It is the largest sub-region in Mesoamerica.  It has a vast and varied landscape, from the mountainous areas of the Sierra Madre to the plains of Yucatan.
references: It is the largest sub-region in Mesoamerica.  It has a vast and varied landscape, from the mountainous areas of the Sierra Madre to the plains of Yucatan. It is the largest sub-region in Mesoamerica. It has a vast and varied landscape that includes mountains and semi-arid plains. It was the larguest sub=region in Mesoamerica.  It encompassed a large and varied landscape ranging from the mountains of Sierra Madre to the plains of northern Yucatan. It was the largest sub-region in Mesoamerica and stretched from the mountains of the Sierra Madre to the plains of the Yucatan. The biggest region in Mesoamerica covered regions from Sierra Madre to north Yucatan. This sub-region was the largest one in Mesoamerica. It had mountains and dry plains in the area. It started at the Sierra Madre and ended in northern Yucatan. It was a small part in Mesoamerica took up land that was varied from the mountains of the Sierra Madre to the somewhat dry flat area of north Yucatan. The biggest sub-region in Mesoamerica, it covered a vast and varied landscape, from the mountainous Sierra Madre to the semi-arid plains of Yucatán. As the largest sub-region of Mesoamerica, it ran from the mountainous regions of the Sierra Madre to the plains of the northern Yucatán. As the largest sub-region in Mesoamerica, is encompassed varying landscapes from mountainous regions to semi-arid plains.