In preparation of my upcoming trip to Argentina I stumbled upon this one:
Full name of site: Railways of the Andes: Ferrocarril Central Andino & Tren a las nubes
Country: Peru and Argentina
Short description of site (also include multiple locations if applicable): These are the 2nd and 3rd highest railways in the world, finishing at 4,818 and 4,220 metres altitude resp. The construction of these railways started in the late 19th, early 20th centuries.
Criteria (cultural, natural, mixed): Cultural (ii)
Outstanding universal value / comparative analysis: The highest railway in the world is the much more recent Chinese Tibet Railway. These 2 Andean railways are an immense triumph of engineering, certainly considering their age. They were instrumental in the mining industry and the opening up of far-flung regions / borders.