Urban gardens are in a unique category as influences from neighbouring spaces are so often non-existent. These enclosed gardens are small to medium sized spaces associated with town and city houses. A design for a completely enclosed space has few restraints, so the result can be as exotic as desired due to little or no relationship to its neighbouring urban landscape. Here the 'outside room' concept is important as the house and garden will need to be strongly linked both visually and physically.
Do you have your own unique style? Do you love the juxtaposition of old and new? If you own an old terrace house, or similar, with the garden completely enclosed then maybe an urban garden adjoining the old house is just what you are looking for!