Garden design theory explains, or should explain, the 'What, Where, Why and How' of making gardens.

From 50 centuries, we can learn about the close relationship between garden design and urban design, because both arts involve the composition of buildings with paving, landform, water, vegetation and climate.

The strengths landscape architecture draws from its garden design heritage include: the Vitruvian design tradition of balancing utility, firmness and beauty; use of the word 'landscape' to mean 'a good place' - as the objective of the design process; a comprehensive approach to open space planning involving city parks, greenways and nature outside towns; a planning theory about the contextualisation of development projects; the principle that development plans should be adapted to their landscape context.

Humphry Repton, the leading garden theorist of the nineteenth century, defined a garden as 'a piece of ground fenced off from cattle, and appropriated to the use and pleasure or man: it is, or ought to be, cultivated and enriched by art'.

In ancient times the ritual, mythological and doctrinal aspects of spiritual space were predominant.

Having lasted for 4,000 years, the use of nature's materials to express ideas about nature may be expected to continue. The best garden designs are produced with an awareness of the art, science, history, geography, philosophy, social habits and construction techniques of their period.

There is much to learn about what could happen in the gardens of the future, should designers wish to learn about the past.