This is a strange site to visit - how do you determine whether you have 'seen' it, when it's made up of thousands of kilometres of track all across the continent?

I consider that I have ticked it off because I walked much of the tracks on my way to Machu Picchu in Peru. But you could so it so many other ways - or even spend years walking different routes and still never technically see it all.

I'm glad it has been added to the list, though. It's a really interesting part of national infrastructure and played a huge part in the ability of the Incans to grow their civilisation and conquer so much of South America.

Will UNESCO be tempted to look favourably upon a submission from the US to list the country's interstate highway system now? :)