Complex sentence: In 2001, Visy undertook the-then largest development in its remarkable history was the construction of a $450 million kraft paper mill in Tumut, New South Wales--the first kraft mill built in the world in 20 years.
Split into simpler sentences: In 2001, Visy undertook the-then largest development in its history, the construction of a $450 million kraft paper mill in Tumut, New South Wales. This was the first kraft mill built in the world in 20 years.