Surah 2:149
"From wherever you go forth, turn your face toward the Sacred Mosque. Surely it is the truth indeed from your Lord. God is not oblivious of what you do."
The Earth is Flat
The Qur'an tells all Muslims to face in the direction of Mecca when they pray. However, this would only be possible on a flat Earth because it is not possible to bow down towards the direction of Mecca when you are on the opposite side of the earth. The author here presupposes a small world, local to Arabia, that is flat. Only in that world view can people everywhere face Mecca.