Step 1: Understanding the Concept:
The Channel Tunnel is a major undersea rail tunnel linking the United Kingdom with mainland Europe. It facilitates high-speed passenger and freight rail services.
Step 2: Detailed Explanation:
The Channel Tunnel, often called the "Chunnel," physically connects Folkestone in Kent, England, with Coquelles in Pas-de-Calais, France. The primary high-speed passenger rail service that uses the tunnel is the Eurostar. The most iconic and highest-traffic route for the Eurostar is between St Pancras International station in London and Gare du Nord station in Paris. While Eurostar also runs services to Brussels and other destinations, the London-Paris connection is its most famous and direct application. The other city pairs listed are geographically incorrect for the Channel Tunnel.
Step 3: Final Answer:
The Channel Tunnel's most prominent connection is between London and Paris.