ドーバー海峡トンネル

１９世紀末には、実際に着工されてたんですね。

An official Anglo-French protocol was established in 1876 for a cross-Channel railway tunnel. In 1881, British railway entrepreneur Sir William Watkin and French Suez Canal contractor Alexandre Lavalley were in the Anglo-French Submarine Railway Company that conducted exploratory work on both sides of the Channel. On the English side a 2.13-metre (6.99 ft) diameter Beumont-English boring machine dug a 1,893-metre (6,211 ft) pilot tunnel from Shakespeare Cliff. On the French side, a similar machine dug 1,669 metres (5,476 ft) from Sangatte.

こちらのサイトに、画像つきで詳細が。
Channel Tunnel - 1880 attempt