Actually, castle heights are in many ways like clusters of multistory apartment buildings that often surround a small patch of open space. Like an elevator shaft, all the rooms that look out onto this space have the same point of view as Rapunzel did, straight down to the ground.

A thousand years ago, they needed a steady supply of aromatic herbs to season not-so-fresh food and to cloak the odors of what that era would dub "the great unwashed."

Fresh clippings of santolina, rosemary, thyme and sage were strewn onto the floors, scattered into bed sheets and stuffed into less-than-clean garments. But when the barbarians swept through the neighborhood to pillage what they could, everyone ran to the castle for protection until the invaders moved on. And that meant there were more unwashed bodies within the castle walls, and the need for herbs was unceasing.

Then somebody got the bright idea of making an herb garden at the bottom of that space within the battlements. There they could grow herbs and greens without venturing out into risky open country. Now these folks could have just grown in rows, but, thankfully, they reached into ancient Celtic art where they found patterns, a lot like large knots of different-colored chords. Those first crafty gardeners decided to lay out the herb garden at the castle in a pattern that could best be seen from high above. It was a bird's-eye view that drove this design.

Today these ancient herb plots of the medieval castles are called knot gardens. Every time the herbs were sheared to generate more clippings to use indoors, the knot pattern was refreshed. Over time they grew more elaborate, larger and yielded more colors and a powerful three-dimensional effect.

When the Dark Ages passed, the knot gardens of castle grounds were expanded outside the walls. In France, these patterns upon the ground grew to many acres in size. In time they evolved into the parterre, which reached its zenith at Chateau de Villandry, the world's most decadent food garden.

One of the greatest truths of garden design is that there are no new ideas; only the applications change. Therefore, gardens thankfully tilled in vacant lots and small plots between buildings should be seen on two planes. First, of course, is the ground plane or the human-eye level. Here the garden must produce vegetables or greens and other edible plants. That is the functional aspect of its existence.

The second plane is called "plan view" by designers. This is the view of a Google Earth satellite photo that shows your home and grounds from above. Inside a castle garden you may not even perceive the pattern at all, and only when looking out a window above does the graphic become apparent.

Imagine what would happen if urban gardeners who live in apartments above began to view these practical cultivations as visual opportunities. If those spaces were laid out in interesting graphic patterns, whether inspired by modern art or ancient knots, they would be productive and beautiful, too.

It's really all about how you lay out raised beds. The parterre at Villandry is all rectilinear in form, with the beds laid out at easy-to-build 90-degree angles. This eliminates the complex knots with their odd angles and curves. Whether it's a simple four-square garden or a detailed parterre, accuracy is what makes them pop when viewed from above.

The beauty of knowing history is that we can draw from ancient ideas and give them modern applications. This medieval knot garden is an idea perfectly tailored to our modern urban plots.