It is perhaps the eighth wonder of our world that despite modern mapping and satellite photography our planet continues to surprise us. Travis Elborough goes in search of the obscure and bizarre, the beautiful and estranged. From the church tower of San Juan, that stands as the sole survivor of a town sunk by lava, to Berlin dug for refuge and espionage, the incredible stories of hidden lairs, forgotten cities and improbable wonders are told. With beautiful maps and stunning photography, this is a fascinating voyage to the world's most incredible destinations