Square Rock Walking Trail is located in Namadgi National Park which is located approximately 30 minutes drive south west of Canberra. As far as I am aware there is no public transport out this way so you will need a car.
The Square Rock trail head starts from a small dirt car park just a few hundred meters past Corin Forest Recreation Facility (or Corin Forest Mountain Resort according to google maps). See map below.
From the car park the walk is approximately 8.5km (2-3 hours) return and although most brochures refer to the walk as easy-moderate it is probably more easy for experienced hikers or for people with an average fitness level.
For the majority of the walk there is not much to see other than trees and scrub land but towards the end of the walk there is a small side trail that take you to Orroral Valley Lookout. This is a nice lookout but nothing special. After a little more walking we finally reached the destination; Square Rock. This collection of hugely oversize rocks is beautiful as are the views available from them. This is a great walk and I highly recommend it for anyone looking for half a day outdoors but nothing too strenuous.
A helpful tip – After a few hours of walking and drinking lots of water I was in desperate need of a bathroom but I am not a fan of using a bush for a toilet plus the drive home from the trail head is at least 40 minutes. As a result before heading home we decided to stop a few hundred meters down the road at Corin Forest Recreational Facility which luckily for me have very clean bathrooms for public use.