Vast Horizons and Formidable Frontiers

The five moments in this challenge

The scenes are shown below — tap a card to reveal its place and year.

1. 

   Round 1 · 1933

   Hoover Dam Concrete Pouring

   Nevada-Arizona Border, USA

   To cool the millions of tons of concrete and prevent the dam from taking over a century to cure, engineers embedded a network of pipes circulating ice water throughout the rising blocks.

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2. 

   Round 2 · 1881

   First Trains on the Darjeeling Railway

   Darjeeling, India

   Nicknamed the 'Toy Train', this marvel of narrow-gauge engineering relies on a series of daring loops and zig-zags to ascend the steep Himalayas without the use of a rack system.

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3. 

   Round 3 · 1495

   Da Vinci Painting The Last Supper

   Milan, Italy

   Leonardo da Vinci experimented with applying tempera directly to a dry wall rather than wet plaster, a decision that caused the masterpiece to begin deteriorating within his own lifetime.

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4. 

   Round 4 · 1450

   Inca Pilgrims at Isla del Sol

   Lake Titicaca, Bolivia

   Revered as the birthplace of the sun god Inti and the first Inca king, this rocky island was heavily terraced and built up as a major destination for religious pilgrimage.

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5. 

   Round 5 · 1324

   Mansa Musa's Caravan Departs for Mecca

   Oualata, Mauritania

   The Emperor of Mali embarked on a pilgrimage accompanied by tens of thousands of subjects and so much gold that his spending in Cairo temporarily crashed the regional economy.

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