1. The Dimensions and Wall of the Har Habayis
Today’s Rambam discusses the structure of the Har Habayis—Temple Mount. In recent news, there has been mention of religious Jews ascending the Har Habayis, but this raises significant halachic concerns. Since people today are not in a state of ritual purity, entering the Har Habayis is generally prohibited. The Rambam begins by giving us the dimensions: the Har Habayis measured 500 amis—cubits—by 500 amis. He notes that this entire area was surrounded by a wall.
This wall is presumed by many to be what we now call the Kaisel Maaravi—the Western Wall—which is part of the retaining walls we see today. While I am not an expert in historical or geographical matters, it seems reasonable that these walls correspond to those described by the Rambam as encircling the 500 by 500 amis area.
2. The Roof Over the Har Habayis
The Rambam adds a fascinating detail: he writes that the entire Har Habayis was covered with a roof or overhang. This is remarkable given the vast span involved. However, commentaries clarify that while much of the area was covered, it does not mean literally every part was roofed over—especially not above areas like the Mizbeach—the altar.
The Mishnah in Pirkei Avos mentions one of the miracles in the Temple: despite wind, smoke from the Mizbeach always rose straight up to heaven. If there had been a complete roof, this miracle would have been unnecessary or impossible, so clearly there were openings above certain sections such as over the altar.
3. The Fire on the Mizbeach and Its Miracles
The Torah describes how fire would descend from heaven onto the Mizbeach. This heavenly fire remained burning even during travel in the wilderness; Rashi explains that a copper cover protected it so it never went out, even when everything was packed up and moved.
This miracle continued through the first Bais HaMikdash, but ceased in the second Temple era—then, only human-made fire was used on the altar. Nevertheless, Pirkei Avos still refers to smoke rising straight up during both Temples, implying there must have been some opening above at least part of the altar area.
4. Construction Details: Arches Beneath Har Habayis
The Rambam also describes how arches were constructed beneath parts of the Har Habayis. These arches were built one atop another underneath certain areas. While he does not specify exactly where or how these arches were placed, their purpose relates to laws of ritual impurity (Tumah).
If there is a grave deep beneath ground level (known as a Kever HaTahoym—a grave in an abyss), its impurity can rise straight up unless blocked by an intervening structure called an ohel—a tent-like space with specific dimensions. The arches created such spaces, preventing impurity from rising all the way up to defile those walking above on top of them.
5. Boundaries and Internal Structures on Har Habayis
Apart from external walls and supporting arches below ground, there were also internal boundaries within the Har Habayis. These demarcated different zones and levels of sanctity within its expanse. Many details about these boundaries and structures are derived from various Mishnayos and other sources throughout Torah literature.
This overview shows how much complexity and thought went into both protecting ritual purity and organizing sacred space on the Temple Mount according to halacha and tradition.