Corin Forrest Park Alpine Slide 

Corin forest park is about 45 min from Canberra city centre. The slide cost $28 for a hour session and you get in about 7-10 goes in that time depending on size of group.
The tow up takes about 2-3 minute and a little wait at the top for the other riders to go. The fast time down the hill is about 40 sec, so I heard.