MegaBus is offering very cheap tickets from Germany to Catalunya. Cologne – Barcelona – Cologne for only 2 EUR! Additional reservation fee 0.50 EUR. You can end the trip in Lyon, Montpellier or Perpignan for the same amount.
June, July and August 2015.
Cologne – Barcelona/Lyon/Montpellier/Perpignan – Cologne.
How to book:
Go to megabus.com and choose routing.