Alicante to Barcelona ferry

Ask it something like this

• Three days in Portugal in October, no flightsA country and a length becomes a chain of real legs
• Cheapest way from Berlin to Prague next weekendA corridor, a lens and a relative date
• Madrid to Barcelona by train for two peopleA mode, a party size and a price for the party
• Greenest way from Amsterdam to ParisThe carbon lens, with the tradeoff spelled out