On many levels, the Sino-Vietnamese border is no place for the faint-hearted.
A 1,350km arc that traverses jungle and mountains, it stretches from the Gulf of Tonkin to a high mountain pass in Yunnan where the borders of China, Laos and Vietnam intersect.
Recent decades have seen it plagued by war, smuggling and simmering tensions between Beijing and Hanoi. It stands as a symbol of ancient and lingering suspicions but also of the promise of peace between two nations whose relationship is one of the most complex in the region.
Improved cross-border highways and railways are opening up new areas of poor northern Vietnam to investment and trade.
Fed up with the high cost of flights between Hong Kong and Hanoi, the most expensive short haul leg in the region? One day you may be able to drive there.
In one very obvious way, too, the border serves as a barometer of the wider relationship. By the end of the year, both sides hope to complete the placing of marker stones along its route. The effort, started after a border demarcation agreement in late 1999, has been a drawn out affair. More than 90 per cent has been completed, but the last few stones are among the most sensitive and prone to dispute.
Officials on both sides acknowledge that completing the physical marking to be an important step in helping to ease broader tensions. On the other hand, they privately warn it is far from clear whether their goal can be met.