The north wall of the expanded Har Habayis was mostly destroyed, and virtually no remains can be seen above ground, besides for a few stones in the northeast and northwest corners. (The Kaftor Vaferach already observed this fact, as he writes (chapter 6) that the northern wall is destroyed, as opposed to the other walls, where he found remains of all the gates mentioned in the Mishnah, see my earlier post about this Kaftor Vaferach.) However, it seems that there are still remains of this wall underground, as the present north wall of the Har Habayis is on the same line as we would make the Herodian north wall be, based on the remains at both corners.
Now, were there gates in this wall, and if yes, how many? the Tavnis Heichal (2:12-13) writes that there were two bridges, leading up to two gates in this wall. One of them was towards the eastern corner; and was used to bring in the animals after washing them (see my previous post, about the Bereichas Yisrael), and one led from the "business district" to the Har Habayis. Now, the source for the first gate seems to be from early non-Jewish (christian) sources, which mention a pool for washing animals next to a gate, called the "sheep gate", which the Tavnis Heichal seems to understand as a gate to the Har Habayis. The Tavnis Heichal does bring a source from Josephus for this paragraph, however this source (Wars 5:11:4) just mentions that there was a pool, called "The Struthion Pool", next to the Antonia fortress, it does not mention anything about a gate or washing animals, and it seems that the Tavnis Heichal just brought it as a proof that there was a pool of water next to the northern wall of the Har Habayis. However, the Tavnis Heichal did not know that there were actually three pools in this area, the Struthion pool by the Antonia fortress, the Bereichas Yisrael by the northeast corner of Har Habayis, and the double pool to the north of them.
The second gate mentioned by the Tavnis Heichal has much better sources for it. The source for this gate is from Josephus, who mentions (wars 2:19:4-5) a gate in the northern wall of the Har Habayis. Josephus is talking about an unsuccessful attack on Yerushalayim by the Romans at the beginning of the war that led to the Churban Bayis Sheini, he writes the following:
"But now Cestius, observing that the disturbances that were begun among the Jews afforded him a proper opportunity to attack them, took his whole army along with him, and put the Jews to flight, and pursued them to Jerusalem... And on the fourth day, which was the thirtieth of the month Hyperbereteus, [Tishrei,] when he had put his army in array, he brought it into the city.... But when Cestius was come into the city, he set the part called Bezesa, which is called Cenopolis, [or the new city,] on fire; as he did also to the timber market...... Thus did the Romans make their attack against the wall for five days, but to no purpose. But on the next day Cestius took a great many of his choicest men, and with them the archers, and attempted to break into the temple at the northern quarter of it; but the Jews beat them off from the cloisters, and repulsed them several times when they were gotten near to the wall, till at length the multitude of the darts cut them off, and made them retire; but the first rank of the Romans rested their shields upon the wall, and so did those that were behind them, and the like did those that were still more backward, and guarded themselves with what they call Testudo, [the back of] a tortoise, upon which the darts that were thrown fell, and slid off without doing them any harm; so the soldiers undermined the wall, without being themselves hurt, and got all things ready for setting fire to the gate of the temple."
From this passage of Josephus, we see that there was a gate in the outer northern wall of the Har Habayis, which was accessible once the newer city (the area inside the second and third wall) was captured. The "business district" mentioned by the Tavnis Heichal seems to be the "timber market" which Josephus mentions together with Beseza, which was north of the first wall, indicating that the market was also in the same place. The Tavnis Heichal seems to understand Josephus's narrative going forward, that the Romans (under Cestius) went from one place to another, making that the market was on the way to the Har Habayis.
[We should mention here Juan Bautista Villalpando, a galach who wrote a commentary on Yechezkel, most of which was devoted to the Beis Hamikdash and the city of Yerushalayim. Most of his ideas are very strange (such as his assertation that the first, second, and third Beis Hamikdash were all identical), however he seems to have influenced the Tavnis Heichal in his discussion of the outer wall of the Har Habayis. He also made these two gates in the northern wall of the Har Habayis, one leading over a bridge to the pool, and one leading over a bridge to the timber market. (See a map of Yerushalayim based on Villalpando's books here.)]
However, from where did the Tavnis Heichal know that these were two separate gates? maybe the road from the market led to the pool for washing the animals, and from there it led up to the Har Habayis? I am not able to find an answer to this question, but I can possibly find a source for there being two gates in the north from Yosifun. (The Sefer Yosifun is brought down by many Rishonim, and seems to be based on a translation of an Aramaic book by Josephus, although many additions and changes were added into it.)
In Sefer Yosifun (chapter 55), he writes about Hurdus building the Beis Hamikdash, and describes the structure. However, his account there is very strange, as it seems to be describing the Heichal in the middle, with four large Ulamos projecting from its four sides, similar to a plus symbol (like this+), and at the edge of each Ulam, he makes a courtyard. This is obviously not how the Beis Hamikdash looked, and it seems that someone misunderstood Josephus's original description of the four porticos on the four sides of the Har Habayis, that surrounded the Beis Hamikdash. (We should note that Rashi, Yoma 23a, mentions these Ulamos of Yosifun.)
The Gemara (Berachos 33b, Pesachim 13b, Sukkah 45a) also mentions these porticos on Har Habayis, and since when the Gemara talks about the Har Habayis, it is referring to the 500-amah square, which had the kedushah of Har Habayis, it must be that these porticos ran along the walls of the square Har Habayis, and not the Migrash or Herodian extension. (The Rambam Hilchos Beis Habechirah 5:1 writes clearly that these porticos were located in the 500-amah square Har Habayis.) Therefore, the courtyards in front of these Ulamos that Yosifun mentions must come from a description of the space in front of these porticos, i.e., the Migrash and the Herodian expansion.
Now, Yosifun mentions four gates in the southern, western, and northern courts. It is commonly understood that one of the copyists or redactors of Yosifun took this description of four gates, which was originally just by the west, and copied it to the north and south. However, it could be that the original text also had these four gates on all these sides, and they were the following: In the west, Warren's gate, the gate above Wilson's arch, Barclay's gate, and the gate above Robinson's arch. The four gates in the south would be the two gates in the double gate, and two in the triple gate, while one of the triple gates must not have had a tunnel leading from it to the surface of Har Habayis, but rather was used to access Shlomo's stables. The gates to the northern court would be the two Sha'ar Harachamim, which exit to the northern part of the expanded Har Habayis, and two more gates in the north wall. If this interpretation is correct, we have a source for there being two gates in the northern wall of the expanded Har Habayis, like the Tavnis Heichal writes.
I should mention that in this part of the present northern wall of the Har Habayis, between the Bereichas Yisrael and the Antonia fortress, there is also two gates, the Bab al-Hittah gate and the Bab al-Etan gate, mirroring the situation that was there when the Har Habayis was first expanded, and it is possible that these gates and the roads leading to them are built on remains from the Herodian era.
I found a possible source for there being two gates in Josephus. He writes (Wars 6:2:7) that the romans, put up banks to attack the square Har Habayis. One of the places they did this was by "the northern building between the two gates", since the northern wall of the square Har Habayis only had one gate (sha'ar tadi), these two gates must be in a different wall. It could be talking about the northern wall of the expanded Har Habayis, however it could also mean between two gates of the Azarah. So, while this is a possible source, it is not definite.
A computer rendering of the two gates in the northern wall and the paths leading to them. I have made the "bridge" to the gate where they would bring in the animals as a tower with stairs, as opposed to a regular "bridge" with steps, since there is not enough space between the Bereichas Yisrael and the gate for that.
I have added sixteen pictures of the third Beis Hamikdash, as well as a new map of it.
My name is Mendel Lewis.
Hashem said to Yechezkel, "Its reading in the Torah is as great as its building. Go and say it to them, and they will occupy themselves to read the form of it in the Torah. And in reward for its reading, that they occupy themselves to read about it, I count it for them as if they were occupied with the building of it. (Tanchuma tzav 14)