Parah, Chapter 3, Mishnah 6. This chapter follows the preparations for burning the parah adumah step by step, and here the Mishnah describes how the kohen and his entourage traveled from the Beis Hamikdash to the place of the burning. The route itself was an engineering project, and every detail of it was designed with one worry in mind: the possibility of an unknown grave lying somewhere along the way.
Let us take the Mishnah's words clause by clause. "V'keves hayu osim", they would construct a ramp, "mehar habayis l'har hamishcha", running from the area of the Temple Mount across to Har Hamishcha; "kifin al gabei kifin", vaults built one tier above another, "v'kipa k'neged ha'oten", each vault of the higher tier aligned over a vault below it rather than over its supports, "mipnei kever hatehom", all as a safeguard against a burial hidden deep in the ground that no one knew about. "Shebo kohen hasoreif es hapara", it was along this elevated walkway that the kohen charged with the burning traveled, "v'hapara v'chol mesa'adeha", together with the cow and everyone taking part in her service, "yotzin l'har hamishcha", all of them making their way out to Har Hamishcha.
Two terms to open
A keves in this context means an inclined causeway, a raised walkway that led down from the Temple Mount area and carried the procession across to the mountain facing it. And har hamishcha, the mountain of anointing (some explain the name as referring to atonement), is Har Hazeisim, known as the Mount of Olives, the site where the parah adumah was burned.
Arches upon arches
What is meant by kifin al gabei kifin? The pathway was not simply paved upon the ground. Its surface rested on a row of curved vaults, each one hollow underneath, and that row was itself carried by a second tier of vaults set below it. The Mishnah then specifies the alignment: v'kipa k'neged ha'oten, every vault of the higher tier came down over a vault of the tier beneath it, and not over the piers that held that lower tier up. The weight of the top level, in other words, pressed onto arches rather than onto stonework running unbroken into the earth. Along the entire stretch of the causeway, then, there was nothing but air between the walkway and the soil.
Why go to such lengths
The reason is kever hatehom, literally a grave in the depths: an unknown, forgotten burial that nobody could identify or rule out. The concern was that somewhere along the route a corpse might be lying buried beneath the ground. Tumah rises, and had the walkway rested solidly on the earth, that tumah could have traveled up through the structure and rendered the kohen and the parah impure without anyone knowing. By leaving hollow space under the entire ramp, and by making sure that the hollows continued upward level by level rather than being interrupted by solid supports, the builders ensured that any tumah rising from below would be stopped and could go no further.
The procession
The Mishnah closes by telling us who traveled this route. The kohen assigned to perform the burning walked along the raised path, and he did not go by himself: the cow was brought with him, as were all those who had a share in helping with the service, all of them heading out to Har Hamishcha, the site where the full avodah of the parah adumah would be performed.