It's a place to become unstressed. People like to be where there are living things. Plants. Fish. Birds.

When they don't have room for large lawns or patios anymore, or they're running out of room for things in the house. By turning a small (outdoor) area into something grandiose, it gives them a feeling of space.

You can have multiple rooms, but they should somehow connect. Add walking paths, little bridges and creek paths.

There are "indicator" plants and there are "indicator people". When you see Cedar, you know there's alkaline, limestone-based soil around. When you see Fly Fishers, you know there's fish around - well, not always.

I teach people about plants.

I suggest that gardeners plant both types of plants. Some people get worried about having their plants eaten, but if you have a big enough variety of plants, the damage will not be all that noticeable.