I should have said ancient Egypt. I was curious because of the ridiculous amount found in the tombs of dead pharaohs. Did they mine it themselves or get it by trade? If they mined it, where/how did they mine it? If they traded it, where/who were they trading it from and where/how did those people mine it?
Edit: Also, did they have a reason other than being ordered by the pharaoh because he thought it looked pretty? Or did they trade it for other goods? Etc?
They got much of it from the next country over, to the south of Egypt, which was called Nubia. One of Nubia's natural resources was gold. The Egyptians conquered Nubia, and that meant that they could extort tribute from the Nubians. If you click on the second picture here, you can see the conquered Nubians offering rings of gold to the king of Egypt, and even kneeling in submission.
For most of its history, Ancient Egypt didn't have a concept of money. That meant that the wealth of the government, or the king, had to be stored in the form of goods: grain, cattle, gold. The more of these things the king had stored up, the more he could use to trade for whatever he needed, or to give to loyal subjects as a reward for good work. It was like having a high balance in your bank account. The gold was commercially valuable regardless of whether the current king thought it was particularly pretty. This is still true today.
You're probably thinking of Tutankhamun, one of whose coffins alone was made out of 110 kilos of pure gold. He was very young and disabled, which means he hadn't conducted any military campaigns to conquer Nubia himself. The gold in his tomb represents some of the accumulated wealth of the monarchy, thanks to the kings that had come before.
(But I just have a BA in history.)