The Ministry of Unification doesn’t feel like the diplomatic nerve centre for one of the last vestiges of the Cold War; past the security checks it resembles an ordinary office, with potted plants. Yet this is South Korea’s main communication link with its hostile neighbour to the north and the unit in charge of planning for a unified Korean peninsula.

A job here isn’t all intelligence and diplomacy. It also involves a daily act of faith: a belief that the two Koreas can agree on a merger that will bring democracy and a free-market economy. “Many people from other countries ask us when we think unification will be achieved – no one can predict this,” Hwang Seunghee, the senior ministry official in charge of unification plans, tells monocle. “We might have to experience more confusion first.”

“Confusion” is putting it mildly. Since South Korean president Park Geun-hye assumed her post in February, the two Koreas have swung from suspended economic ties to threats of attack. Hardly a week goes by without the regime in Pyongyang bristling at perceived provocations and promising to destroy South Korea and its ally, the US.

South Korean leaders talk about a unified Korea in terms of national identity; working towards “peaceful unification” is part of the constitution. Inside the Ministry of Unification, the official line is that the existence of two Koreas is an aberration. “Our history as a divided peninsula is 60 years but that’s not long considering the 1,300 years of history we have as a unified country,” says Hwang. Benefits would come with integration: access to the North’s natural resources, economies of scale and military-spending cutbacks.

But polls show that the public has grown sceptical. In the 1990s, more than 90 per cent of South Koreans felt unification was needed; that figure has fallen to around half. Young South Koreans baulk at the prospect of footing the bill for a poverty-stricken country as they compete for jobs, while few think of North Koreans as kin. “It wouldn’t work – we are too different culturally,” says Kong Kyung-sik, 31, a barista at a Seoul café.

How to pay for the merger is a divisive issue in South Korea because nobody knows how much it will cost. The Korea Institute for National Unification, a state-funded think tank, estimates that the bill for the first year of integration would range from 55trn to 249trn South Korean won (€37bn to €170bn). Finance Ministry models predict that spending would continue for a decade; experts say it will go on longer.

“For Korea, it will be more difficult than it was for Germany,” says Hanns Günther Hilpert, economist at the German Institute for International and Security Affairs in Berlin. “Korea’s separation has lasted longer and differences in North and South Korea’s systems are larger.”

Seoul favours a gradual, non-confrontational integration – but what if North Korea’s regime collapsed? Experts predict a refugee crisis of unimaginable scale. “We have a contingency plan to block North Koreans from crossing the border into South Korea or China, to prevent a mass exodus,” says Hwang.

Integration is a hard sell. Over the years the Ministry of Unification has promoted the cause in schools and TV shows with pro-unification storylines. Last year the ministry tried something new: it asked for donations to a unification fund. A potter was commissioned to produce large, white jars modelled on traditional hang-ari, used by Koreans to save for hard times. Alas, they drew criticism at home and derision from the North. “We have one for North Korea,” says Hwang, “but we haven’t had chance to give it to them.”

Therein lies a key frustration for the ministry: much depends on North Korea’s co-operation. So far, neither engagement nor punishment for bad behaviour has worked. Still, the ministry is undeterred. “Unification isn’t something you achieve in a moment,” says Hwang. “It’s a process.”

A reunited Korea would face many challenges but, amid the problems, there could also be some significant opportunities.

Property boom
With vast tracts of land in the north completely undeveloped, it could be time for a canny investor or two to build holiday homes along the shores of the Korea Bay. They would appeal to China’s growing middle classes looking for overseas property.

A new capital
North Koreans may struggle to accept the city as their new capital; likewise, southerners are unlikely to be swayed by Pyongyang’s charms. A compromise might have to be found.

An Olympic bid
After the success of the Seoul Games in 1988, a reunited Korea could take advantage of the numerous mountain ranges in the north and make a bid for the Winter Games.

The Kim Jong-Il film school
Given the late North Korean leader’s love for the cinema, a newly open north could establish Asia’s premier film school, attracting talent from across the region and complementing Busan’s successful festival in the south.

World’s most beautiful museum
Once the landmines have been cleared and the watchtowers on both sides of the border have been dismantled, the demilitarised zone (DMZ) could become a stunning outdoor museum.