The Sanhedrin, instituted within the Torah, was the Supreme Court of Israel. There were three levels of this highest level of the Judicial System. The highest was known as the Sanhedrin Gedolah (the Great Sanhedrin) and they met within the Lishkat haGazit (the Chamber of Hewn Stone) which was within the Beit Avtinas (House of Avtinas). This building was located on the southeastern corner of the Azarah (the Inner Courtyard of the Temple). The building was divided into two sections. The section closest to the Azarah was the sanctified section of the building while the section closest to the Cheil (the 10 cubit wide stabilizing platform that surrounded the buildings and gates adjoining the Azarah) was the unsanctified section. The Cheil had a lower sanctity than the Azarah. In the unsanctified section of the building is where the Sanhedrin Gedolah sat. The overall building (Beit Avtinas) had the kedushah (sanctity) of the Azarah. There were 71 judges to the Sanhedrin Gedolah.
The second court, the Sanhedrin Ketanah (the Smaller Sanhedrin) sat in the Cheil outside the eastern gate of the Ezrat Nashim (Court of the Women). This court had 23 judges and tried cases not requiring death penalties.
The third court sat off the Temple Mount just to the east of the Southern Steps and was known as the Beit Din haGadol (the Great Beit Din - House of Judgment). This building was located with a portion of the plaque that was on the building. The court had 3 judges.