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Siemens

Øresund Strait (from Region Skåne press release)

Fixed HH Link (marked with circle) environs. It is from Region Skåne press release supplements.

CREC press news release

Firth of Forth Tunnel as proposed by Scottish Greens.  image: Deltix Transport Consultancy (from Rail for All report commissioned by Greens)

Barcelona L9 Metro line Vinals, CC BY-SA 3.0, via Wikimedia Commons

Altona tunnel Hamburg, from Implenia

HS2 Chiltern Tunnel South Portal (image by HS2 media centre)

HS2 Chiltern Tunnel South Portal wide view (image by HS2 media centre)