Maybe she's born with it. Maybe it's Scott's Cheap Flights.
Heads up, these fares also work as an open-jaw if you'd like to fly into one city and depart from another. Also, some routes may have an overnight layover in London one way.
Not every origin city has availability to every European city, but we found most routes work. We've found as many European cities as we can, though there may be even more out there. Play around with Google Flights to see what works best from your city. The fares listed are the lowest we could find to Madrid.