Held on a site three times the size of New York’s Central Park, state media reported that the event would feature exhibitions from more than 110 countries or international organisations.

In addition, 11 foreign leaders or their special envoys are expected to join President Xi Jinping to attend the inauguration ceremony on Sunday.

Most significantly, the delegation is expected to include senior Vatican officials amid a thaw in relations following an agreement on the appointment of bishops.

The five-month expo will be held in Beijing’s Yanqing district at a site 74km from the city centre which will also host some events of the 2022 Beijing Winter Olympics.

Although the list of participating countries has not been disclosed on its official website, the organiser expects to attract 16 million visitors.

Just under two weeks before the opening, the South China Morning Post travelled past the Great Wall along the newly built roads linking Yanqing with the city to explore the 960-hectare (2,372-acre) site.

At the time, some 8,000 to 10,000 workers were putting the finishing touches to the edifices and gardens, according to Wu Gang, the deputy director general of the expo’s coordination bureau.

The site had previously been occupied by two villages with a combined population of 2,000 people and Wu said the total cost of resettling the villagers and building the expo site had come to 20 billion yuan (US$2.9 billion).

As with many major Chinese projects, it is unclear how much of this was made up of construction costs, but by way of comparison the Winter Olympics has a reported budget of under US$3.9 billion.

The event has the theme of “live green, live better” – a strong environmental message in keeping with the government’s drive to tackle its notorious pollution – but also draws heavily on Chinese traditions.

“It is to demonstrate Chinese horticulture over thousands of years,” Wu said. “As Xi Jinping said ‘green mountains and clear water are equal to mountains of gold and silver’, the country advocates harmonious coexistence between humans and nature.”

There will be at least 80 garden pavilions and buildings on the vast site of the Beijing expo, and three of them – the China Pavilion, International Pavilion and Plants Pavilion – will provide the main focus of interest for visitors.

The China Pavilion – a building inspired by Ruyi, the traditional Chinese jade ornament symbolising good fortune – will be the main landmark for the event and contain around 20 pavilions representing different Chinese provinces and their distinctive horticultural characteristics.

Next to the China Pavilion is a large green field with 34 outdoor garden pavilions – one for each mainland province or region as well as Hong Kong, Macau and Taiwan.

The Hong Kong one has been decorated by the city’s famous neon signs set between living green walls.

Ashley Zhu Minming, the Hong Kong project manager, said the display would also include four of the most common plants from the city, including ones that can easily be spotted on the streets.

But the sword ferns they had brought up northern China died during a spell of freezing weather earlier this month, forcing them to be replaced with a new batch of ivy trees.

About a 20-minute walk away is the International Pavilion, which stands with 94 “blossoms” stretching up to the sky to create a sea of flowers.

No access was allowed during the visit but it appeared that much construction work remained to be finished before the official opening.

Next to it are another 41 garden pavilions by countries – including North Korea, Pakistan, Kyrgyzstan and Sudan – and international associations showing different aspects of their countries’ cultures.

For instance, the French pavilion will display a model of the Eiffel Tower alongside the plants and even has a resident bakery expert, Raphaël Bornert, who said: “We will provide fresh bakery including croissants and various pastries, as it is an important part of French culture.”

The International Horticultural Exhibition was first held in 1960 and since then more than 20 editions have been held in various locations in Europe, Asia and North America.

This is only the second time that a Chinese city has hosted the event with the first time being held in Kunming, the capital of the southwestern province of Yunnan, in 1999.

Niek Roozen, director of the Netherlands pavilion, was busy setting up the garden with the national flower tulips and other varieties of flowers and plants. Information boards and garden roofs will also be on display to show how the Dutch integrate nature in their city planning.

The veteran landscape architect took part in Kunming’s exposition in 1999.

“It is a big difference with huge development. It is very impressive here,” he said. “It is very interesting to see how China has developed.”

Roozen, who runs an architecture company in Shenyang in northeastern China, has worked on various greening projects around the country.

The Netherlands will host the next international horticultural exposition in 2022 in Almere, near Amsterdam, but the planned expo will be around one-sixteenth the size of the Chinese event.

But Roozen said large-scale projects of this type could bring lasting benefits to the hosts.

He said: “It is a big investment but not a one-off one … We will redevelop the exposition site to a new town. People will live there and all kinds of pavilions will be houses in the future.”

Some of the pavilions built in Beijing will be used as venues for the Winter Olympics while other parts of the site will be preserved as a green space for residents.