A Modern Garden dosen't necessarily mean space-age and come with the same price tag, it simply means that it stretches the bounderies from what most people would call a traditional garden, ie: a lawn, a patio, and plants on the border.  A Modern Garden may incorporate more modern styles and structures, with the use of maybe a sculpture, the use of glass and attractive lighting but to name a few. 

A Modern Garden simply breaks free from tradition and embraces everything new and exciting, basically do not be afraid to try new ideas and combine them together to form something away from the norm. 

Building a Modern Garden does not mean you have to build something that is near impossible it just means you are creating your own individual style.