This is Barcelona and at an ungodly hour of the morning.

How reliable are taxis there in terms of fairness in pricing? In some cities - Athens comes to mind - we were advised to book a specific cab through the hotel concierge, who gave us the price it should cost and the taxi number to look for (this was the evening before), and we were told to pay nothing else and to be sure to take the taxi that had been booked. Worked perfectly.