By Frederik
Pleitgen, CNN
December
22, 2014 -- Updated 0618 GMT (1418 HKT)
(CNN) --
Juergen Todenhoefer's journey was a tough one: dangerous, but also eye-opening.
The author traveled deep into ISIS territory -- the area they now call their
"caliphate" -- visiting Raqqa and Deir Ezzor in Syria, as well as Mosul
in Iraq.
Mosul,
Iraq's second largest city,
was taken by ISIS in a Blitzkrieg-like sweep
in June.
Todenhoefer
managed to visit the Mosque there where the leader of ISIS,
Abu Bakr al-Bagdadi, gave his only ever public address.
And he saw
the realities of daily life under ISIS, with
all shops having to close for prayers in the middle of the day.
"There
is an awful sense of normalcy in Mosul,"
Todenhoefer said in an exclusive interview with CNN.