Janjur Qom was the Homeworld of the Prophets. That is until it was destroyed by a supernova and all the Prophets had to board the Eiffel Tower and escape, apart from the ones who were clever and thought the Forerunners were too stupid to build ships and that the Eiffel Tower was in fact just a tower. So, in short, the Prophets would have been wiped out if they were all clever. Hmm.
Janjur Qom was replaced by High Charity which became the Prophets new home as well as the new resting place for the Eiffel Tower. However, even that was destroyed too, and the Prophets were soon reduced to near-extinction.