In 2 Samuel 5:9 we read:
9 So David lived in the stronghold, and called it the city of David. And David built all around from the Millo and inward.
We see this term “the Millo” also mentioned in a handful of other places.
So, what is the Millo?
Well, that’s where this gets a wee bit complicated.
We’ve got three verses and some archaeology that all help to give us some idea. First off, we have the verses 2 Kings 12:20 and 2 Chronicles 24:25 which both tell about the assassination of Joash, King of Judah:
20 And his servants rose up and formed a conspiracy; and they struck and killed Joash at the house of Millo as he was going down to Silla.
25 …his own servants conspired against him… and they murdered him on his bed.
Because he was assassinated in his bed and in “the house of Millo” these verses seem to tell us that the king lived in the house of Millo.
Remember that. We’ll come back to that idea in a moment.
Next, let’s look at the final verse which helps us, 2 Chronicles 32:5:
5 And he resolutely set to work and rebuilt all of the wall that had been broken down and erected towers on it, and built another outside wall and strengthened the Millo in the city of David, and made weapons and shields in great numbers.
That verse is talking about King Hezekiah’s preparations to defend Jerusalem. Nestled in the middle of a description about how Hezekiah was fortifying the city, we can pretty safely say that the Millo was some sort of fortification.
Now, let’s take a look at the archaeology that can help us out here.
Not too long ago, an archaeologist in Jerusalem discovered what she thinks is the remnants of the Palace of David and the Millo. She discovered two different remains of connected buildings.
The first, she called the Large Stone Structure. It’s shaped like a large palace, and thanks to some hints from the Old Testament, she thinks it might have been King David’s palace.
The second, she called the Stepped Stone Structure. It’s connected to the Large Stone Structure and looks like a large wall bending inwards, like a rampart (you can look up pictures of the excavation; it looks neat). It seems to be some sort of retaining wall, something used to keep all the dirt and debris behind it from moving and shifting. She thinks that this retaining wall/fortification was likely the Millo.
And remember how 2 Kings 12:20 mentions “the house of Millo”? Well, that archaeologist believes this is because the palace connected to the Millo could be called the house of Millo.
There’s also another theory I read which makes the claim that the Millo might have been located a bit farther away, in an area known as the Gihon Spring.
Also, many scholars think that “Millo” comes from the Hebrew word ml’, which means “to fill”. This might be in reference to filling with earth (like an earthen fortification), or some think it means the Millo had something to do with water (like, “to fill with water”).
Overall, we don’t know exactly what the Millo was, but it seems very likely that it was some sort of fortification. Plus, it must have been in the city of David and was likely nearby, if not part of, the king’s palace.