[dario]

Thanks to Albula and Macmatt for their proposals and for the motivations.
Of course, as far as Switzerland is concerned, we could add the Rhaetian Alps network, which has also applied to UNESCO as Heritage Site.
I would be careful to add any modern engineering wonder such as tunnels and high-speed lines.
Now the new Loetschberg base tunnel is an engineering wonder more than a historical railway wonder.
The Channel Tunnel and the Great Belt link and the Oresund link between Denmark and Sweden have broken the isolation of the respective Countries, and created an enlarged European Raiway Network.
Bye from Dario