In the present-day walls of Har Habayis, there are two types of stones from the time of the Beis Hamikdash, one from the time of the first Beis Hamikdash, and one from the times of Hurdus. The stones are mostly between three and four feet tall (approximately one meter), and around five feet (1.5 meters) thick, but their length has no standard size, with some stones being very short and some being very long. 

   Each course of stones is set back a little from the course under it. This was done to strengthen the wall, since these walls were very tall, up to 100 meters, and had to withstand the pressure of the dirt fill of the Har Habayis. These setbacks are generally between one and a half and two and a half inches (three to six centimeters), while in the east wall, since the wall was taller, (because it started on a lower level,) they are between three and four inches (7 to 10 cm), and in one course, the setback is six inches (15 cm).

    The Gemara in Zevachim (54a), when discussing that there was no yesod on the south and east sides of the Mizbeach, asks a question. If there was no yesod under part of the Mizbeach, how could a bird Olah be offered there? The bird Olah's blood must be sprinkled on the upper half of the mizbeach, and it was preferably offered on the southeast corner of the Mizbeach, but since there is no yesod, the blood is just going to go on the floor? The Gemara answers, that there was a piece sticking out of the Mizbeach in that corner, for the blood to go on. (This is how Rashi explains the Gemara. Rabbeinu Tam explains it differently.) Based on this Gemara, I have added this Piece to the Mizbeach.