A newly released video explores an extraordinary proposition: a railway crossing Afghanistan that could ultimately connect western China with Iran and markets farther west.

It is easy to understand the appeal. Afghanistan’s geography has long been described principally as a constraint—landlocked, mountainous and situated between competing powers. A functioning trans-Afghan railway could turn at least some of that geography into an advantage, giving the country a potentially important role in regional trade while reducing transport costs, opening markets and creating much-needed economic activity.

Having worked on infrastructure projects in Afghanistan over the years, however, I do not underestimate the distance between a compelling map and a functioning railway.

The engineering challenges alone would be formidable, particularly if any connection involved the Wakhan Corridor and its exceptionally difficult terrain. Financing, security, political recognition, cross-border agreements and the coordination of different railway systems would all present further complications. Afghanistan also offers many reminders that building infrastructure is only the beginning: it must subsequently be operated, maintained and protected, with revenues sufficient to sustain it.

The video’s presentation sometimes runs ahead of what has actually been agreed or financed. This should therefore be understood as an exploration of a possible corridor—not an announcement that China has committed to build it.

Still, the underlying idea deserves attention. Afghanistan urgently needs infrastructure capable of connecting its economy to those around it, and few countries possess China’s experience in delivering ambitious transport projects across difficult terrain. If anyone is likely to contemplate an undertaking of this scale, perhaps it is China.

“Impossible” may therefore be too strong a word. But between possible and bankable—and between bankable and built—lies an exceptionally long railway.