The walled city of Avila, Spain, as seen from the Mirador de los Cuatro Postes. -- Photos courtesy of Tourist office of Spain

The storks build their nests on it, locals derive income from it, and tourists travel for miles to see it. So why would anyone ever want to tear down the perfectly preserved medieval wall that circles this city?

Obviously officials weren't thinking about tourism in the 19th century. They wanted to modernize by destroying the 800-year-old structure in order to build magnificent boulevards. The only thing that stopped them was a lack of resources. "There weren't enough people to do the job and they couldn't pay them, that's why the wall is now preserved," explains tour guide Blanca Solana.

Today, the walled city of Avila, 112 km north west of Madrid, is a UNESCO world heritage site and a popular tourist destination. But in the 12th century, when King Alfonso VI ordered the wall's construction, its main purpose was to keep out the Moors.

It worked, due in part to its formidable dimensions: 10 metres high, three metres wide, with nine fortified gates and 88 cylindrical towers, all of which stretch around the city for 2.5 km. No wonder it took nine years to build.

Our first glimpse of it is from the Mirador de los Cuatro Postes (the four columns viewpoint) on the outskirts of the city, where you can see the west, north and south portions of the wall and the buildings within it.

We enter the city via the Puerta del Carmen (Carmen Gate), which is located close to our hotel, the Parador de Avila. The 16th-century structure, once the palace home of the wealthy Henao family and later a barracks for the guardia civil, has a lovely courtyard garden which contains a granite boar of Celtic origin. The Parador is just one of 60 buildings of historic interest in this city of 20,000 people.

Life is different inside the wall. For one thing there's a perceptible air of tranquility. There are few cars on the roads so it's quiet -- and safe. Maybe it's psychological, but the wall seems to envelop the city with a sense of security. "Oh yes," Solana confirms, waving her hand as if to say this is the last place you'd ever be robbed. "You can walk at night. It's very nice."

A walk during the day is nice, too, and the sunlight makes it easier to detect the finer details in the wall, which is composed of stones from old Roman cemeteries. Outside the Puerta del Alcazar, Solana points out an upside down inscription on one cemetery stone. "The mudejares (Muslims permitted to live under Christian rule) who built the wall couldn't read," she explains. In other places, bricks with rectangular indentations, used by the Romans for burning incense, can also be found.

From here you can see the apse of the cathedral which is embedded in the wall, providing an additional physical barrier -- as if one were needed. It's worth taking a stroll around the wall's outer perimeter which affords several interesting perspectives.

Another vantage point is from the top of the wall. At one time it was possible to walk the entire way around, now just a few sections are open. After paying a small admission, we climb the steep stairs on the eastern side that lead to the top, and are rewarded with views of the surrounding plains and some historic buildings such as the third-century San Vicente church.

Farther away is the Monasterio de La Encarnacion, a 400-year-old convent where St. Teresa spent 29 years of her life. Avila has become a place of pilgrimage thanks to the 16th-century nun -- a reformer of the Carmelite Order, who established 32 monasteries, and is best known for her lectures and books on prayer, spirituality and mystical theology.

A popular story concerns the re-opening of her coffin after her death in 1582. On at least two occasions, months after she was buried, Teresa's body was found, "in perfect condition, uncorrupted and with a beautiful smell of roses," according to Solana.

Today in Avila you can see the saint's finger, and other relics, on display in the museum next to the Convent of Santa Teresa built over the site of her childhood home.

"Teresa is everything to us," concludes Solana. Even local pastry shops honour their beloved saint with a sweet egg-yolk cake they call "Yemas de Santa Teresa."

The Basilica de San Vicente is just one of the many centuries-old attractions in the city.

Unique experiences are many in the land of stones and saints.