I visited Harlow Carr Gardens with the family and have written a general review “here.”:http://www.silvertraveladvisor.com/review/attraction/204553-review-rhs-garden-harlow-carr
These are tucked away behind the kitchen garden and tend to be quieter than the rest of the gardens.
The hidden garden is hidden away behind a tall beech hedge. Unfortunately the gate leading into it was locked when I visited.
The scented garden is next to it and is a small garden tucked away in the far north east corner of the gardens It is planted with old fashioned roses, scented herbaceous plants and grasses. for those wanting a hidden spot, there is a very attractive seating area at the end of a Wisteria tunnel.