20 k's from town still has you in the 'burbs
BFP is nice, as per Aardvark's suggestion. IME it's extremely busy on weekends.
There's also the Boondall Wetlands;https://www.brisbane.qld.gov.au/sites/d ... ds-map.pdf
Nice but take plenty of mozzie repellent. It may also be pretty soggy after the recent rain.
There are various wooded areas around Brisbane that are pleasant (e.g. Daisy Hill Conservation Park, Mt Gravatt etc) but not startling, and none of them are very big.
One of my favourite walls in Brisbane is actually an urban one; the River Walk from Hamilton to the city. There are some nice vistas, particularly from Teneriffe to Kangaroo Point.