Guests wave at a train that has passed through a new tunnel during the opening ceremony of the NEAT Gotthard Base Tunnel, the world&amp;#39;s longest and deepest rail tunnel, near the town of Erstfeld, Switzerland.&amp;nbsp;The 57.1-km (35.5 mile)-long Gotthard Base Tunnel, 17 years under construction and designed to last a century, is part of a 23 billion Swiss franc ($23.1 billion) infrastructure project to speed passengers and cargo by rail below the Alps, as much as 2.3 km (1.7 miles) under the mountain chain, which divides Europe&amp;#39;s north and south.
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