WE ALREADY know that traveling by bus is the greenest way to travel, but now have proof that it is also the cheapest.

Wanderu, a new bus-and-train travel booking site, created a multi-city journey to 15 European capitals for less than $400 if you plan in advance — if not, the price is closer to $600).

Here is the loop (starting in London) that they offer for that price:

Here is the breakdown of the bus tickets:

For those of you not interested in such an intense trip, Wanderu is still an amazing resource to find cheap bus and train tickets. For example, you can find a bus deal from Paris to Amsterdam for $20, and there are trips from Berlin to Vienna going for about $23.