3,863. The Beis Hamokeid

Hilchos Beis HaBechirah 5:10

Outside the courtyard to the north there was a large building between it and the cheil. This building had a dome and was lined with stone outcroppings. This building was called the beis hamokeid; it had an entrance to the courtyard and an entrance to the cheil. This building had four chambers, two of which were holy and two of which were secular. Dividers separated the holy chambers from the secular chambers. In the southwest was the sheep chamber, in the southeast was the chamber of those who made the showbread, in the northeast was where the Chashmonayim hid away the stones of the altar that was defiled by the Greek occupiers, and in the northwest was the descent to the mikvah.

Hilchos Beis HaBechirah 5:11

A person who went from this chamber down to the mikvah followed a winding staircase that passed under the entire Temple. Candles were lit on either side all the way to the mikvah. There was a hearth there, as well as a lavatory. If the lavatory was locked, then one knew it was occupied.