The Great Wall of China, the Victoria Falls in Zambia or the old downtown of Quedlinburg in Germany. All of them are spectacular locations. But why are they on the UNESCO World Heritage list? How did these attractions and natural wonders make it onto the VIP list of Very Important Places, while others - like Bochum's city center - did not?

Places that want to make it onto the UNESCO list have to fulfill very detailed criteria of uniqueness, but more on this later. The first hurdle for prospective candidates is the nomination.

Nations make suggestions

Every country has to come up with a list of potential candidates it considers World Heritage-worthy. In Germany's case that task falls to the 16 states. They have suggested three sites this year: Hamburg's "Speicherstadt" (warehouse district), the cathedral in Naumburg and its surroundings, and two sites of the transnational "Viking Monuments and Places."

There's a total of 36 nominations this year from all around the globe. Among them are the aqueduct of Padre Tembleque in Mexico, the rock paintings in the Saudi Arabian city of Ha'il and the Forth Bridge in Great Britain. Singapore, with its Botanic Gardens, and Jamaica, with the Blue and John Crow Mountains, have nominated locations for the first time this year.

Preservationists decide

The countries' nominations go to an independent expert panel. The International Council on Monuments and Sites (ICOMOS) studies the thick application folders containing all relevant data and makes their recommendations. The candidates in the natural phenomena category are examined by the International Union for the Conservation of Nature.

Let's stay with the German example. Hamburg's Speicherstadt convinced the preservationists, so they recommended it for inclusion in the World Heritage group. The Naumburg Cathedral wasn't so lucky, because the application lacked conclusiveness and persuasiveness, according to the judges. But Naumburg's residents haven't given up and are still hoping to snatch a spot on the list.

The UNESCO World Heritage Committee decides

That's still possible, because the UNESCO World Heritage Committee can override the preservationists' recommendations. At last year's conference in Doha, the decisions of the committee were heavily criticized, and was accused of including sites on the list for political reasons.

This year's committee head is Maria Böhmer, a minister of state in the German Foreign Ministry, primarily responsible for cultural relations. She wants to refute the negative impression.

"A World Heritage Site has to be of extraordinary and universal value to humanity, not just to a single country," she said. Böhmer also wants to make the work of the ICOMOS experts more transparent.

One-sided list

The application process takes at least 18 months and is highly complex. This has led to the fact that World Heritage Sites are mostly found in Europe, North America and Asia, since other continents lack the personnel or know-how to make the application. The result: 48 percent of all World Heritage Sites are in Europe or North America, while only 9 percent are in Africa.

"The difference mostly comes from the fact that certain world regions contribute an extremely high number of nominations," Katja Römer, spokeswoman for the German UNESCO-Commission, said. "The committee wants to mitigate this imbalance, for example by supporting African countries in drafting the elaborate application dossiers."

The committee that makes the final decision on which sites will be included consists of experts from 21 nations. At the annual conference, they check whether the nominations fulfill at least one of the ten criteria on the World Heritage List.

Beauty, significance, uniqueness

But there is one basic prerequisite: "To be included on the World Heritage List, sites must be of outstanding universal value," it says on UNESCO's website.

Sites like monuments or buildings often have to be considered "a masterpiece of human creative genius," which would be a criteria to fulfill for Hamburg's Speicherstadt. The site must also represent a certain type of architecture or technology, a cultural tradition or a lost culture.

A natural heritage site, meanwhile, should be an area "of exceptional natural beauty and aesthetic importance." The Blue and John Crow Mountains in Jamaica would fall into this category.

The criteria are vague. And they have to be, the German UNESCO Commission says. After all, the World Heritage List is supposed to mirror the world's diversity. That's why it will keep including sites as varying as the silver mines in Potosi, Bolivia and the caves on the Indian island of Elephanta.