Stay in my garden. It's a decent sized garden and so far we have only let our 5 month old neutered boy out when we are with him. He occasionally shimmy's up the fence to get to behind the neighbours bins (goodness knows what is fascinating behind them!).
When he does this we bring him in. When he comes in without a fuss he gets a treat.
In the main he just mooches about, bounces on the trampoline and sits under the bbq watching for passing flies and leaves.
He has a floor to ceiling cat tree indoors so gets the chance to climb and he has a mean technique for getting up the banister.
If we persist will he get it? There's a busy road about 50 yards out of the estate so we can't let him roam but he seems to really enjoys the fresh air.