ynet reports that underneath the Megiddo Prison (opposite the main Megiddo archaeological site), a church including an altar and several mosaics dating back to the third or fourth century were found.
The mosaics even include text, mentioning several names and the fact that they are dedicated to Christ. Neat! The dig was mostly done by prison inmates, by the way, naturally supervised by professional archaeologists.
Here's the story in Ha'aretz