Excavations under this site show it was built upon a noble Etruscan-style residence from that time and below that are early Iron-Age huts (ninth Century BC), like those on the Palatine. A cup excavated from the site was dated to about 625 BC and had the word REX (King) on it (this cup is on display in the "Museo Nazionale Romano Terme Di Diocleziano"). It's been rebuilt many times but the general plan we see today is *Early* Republican (after 509 BC). Rebuilt after fires in 210 BC, 148 BC and 36 BC when they used solid marble floors and walls and other solid rock blocks. It later withstood the fires of 64 AD and 191 AD.
The Regia was a very sacred place where the Pontifex Maximus (Pope) had his official headquarters. It's where he and his Pontiffs (priests) held official meetings and stored their records. Julius Caesar was the Pontifex Maximus from 63 BC until his death in 44 BC.
The largest room is believed to be the "Temple of Mars" (Sacrarium Martis). This temple housed the Hastae (sacred spears/lancers consecrated to Mars) and the Ancilia (shields in a figure-eight like shape). The God Jupiter (father of Mars who in turn was the father of Romulus and Remus) sent down from heaven an ancilia/shield as a gift to Numa Pompilius. Numa was so afraid that the Ancilia would be stolen, he had eleven perfect copies made. This way no one would know which one was the actual divine Ancilia. It's *assumed* that the shields hung on the walls in the Temple and the spears were either hung or somehow fastened to the circular shrine/altar or hearth(?) within the Temple.
Before going to war the General leading the army went into the temple and rattled, shook or moved the spears, while saying "Mars Vigila" (Mars Awaken). The God Mars would then lead the army to victory. If the spears ever vibrated/shook/rattled/moved on their own it was a bad omen of something terrible about to happen to Rome. I've read that possibly that the spears were so *delicately balanced* that a very minor earthquake or rumble could vibrate them, like a primitive seismograph. *OR* perhaps even a very loud clap of thunder could get them to vibrate?
Next: Part 10: Summary