A $1 million zip-line course has been strung between the towering eucalypts of the Illawarra Fly Treetop Adventures site at Knights Hill.

More than 65 "zippers" road-tested the attraction at the weekend.

On Monday, Kiama MP Gareth Ward and Mayor Brian Petschler oversaw a ribbon-cutting ceremony marking the attraction's official opening.

Destination Wollongong's Matt Davidson said the course would give Sydneysiders a new reason to travel "south rather than north".

"There's no zip-lining product in the Illawarra, so it certainly fills a gap," Mr Davidson said.

The course includes two suspended bridges and three zip-lines, with integrated cables spanning 247 metres.

At its highest point, it towered 34.8 metres - 10 storeys - above the ground, giving it claim to the title of Australia's highest zip-line, site general manager Neredith Elliott said.

"The [tour] allows you to sail through the treetops and soak up the breathtaking panoramic views - from the lush treetops right out to the Pacific Ocean," she said.

Tours take about 1½ hours and cost $75 for adults and $45 for children (discounts for booking online), with the treetop walk included. Guides will speak about the area's environmental credentials, with the focus on "medium-adrenaline" eco-tourism, rather than thrills.

UK-based tourism behemoth Merlin Entertainments Group bought the Knights Hill site in 2011 as part of a takeover of the James Packer-controlled Living and Leisure Australia. Merlin owns Madame Tussauds and is the world's second-largest tourism operator, after Disney.

The expansion has created 10 part-time and seasonal jobs.