Someone else can check the 2 Santiago de Compostela routes!
I just checked.
The furthest distance between sites on the route is 1,208km (Santiago - Basilique Notre-Dame, Chalons en Champagne) but that is across two separate WHS
The furthest distance in France is 814 km/ 506 miles (Ameins Cathedral - Eglise Paroissiale, Gavarnie nr. Mt Perdu)
In Spain the distance is slightly shorter 656 km/ 407 miles (Santiago - Canfranc)These ones will make it in on the 1,000km +
Mountain railways of India 2,179km/ 1,354 miles (Nigrili - Shimla)
The Frontiers of the Roam Empire clocks in at 1,350 km /839 miles (Antonine Wall, Clydebank Bavarian Limes, Hienheim on the Danube)
New Zealand Sub Antartic Islands 1,010km/627 miles (Bounty Islands - Auckland Islands)These are short of the mark
Rock art of Iberian Penisula clocks in at 701km so is just short.
Imperial Palaces of the Ming and Qing Dynasties in Beijing and Shenyang is also short at 631km
NB. I can't work out if the Gondwana Rainforests of Australia will qualify as alot of the co-ordinates are incorrect on Google Earth. I will see if I can work it out soon. At the moment the biggest distnace is 450km but 13 sites are not mapped properly.