Gemara Sukkah 51b: “He who has not seen Jerusalem in its splendor, has never seen a beautiful city in his life. He who has not seen the Temple in its full construction has never seen a glorious building in his life. Which Temple? Abaye, or if you want, R. Hisda said: This refers to the building of Herod. What did he build it from? Rabbah said: Of yellow and white marble. There are those who say: With yellow, blue and white marble. The building rose in tiers in order to provide a hold for the plaster. He intended at first to overlay it with gold, but the Rabbis told him, Leave it alone for it is more beautiful as it is, since it has the appearance of the waves of the sea.” (English translation from sefaria.org.)
I thought it was interesting that Herod, known for his cruelty and ruthlessness, managed to build the most beautiful building in the world.
Who was Herod? The gemara in Bava Basra 3b-4a says that Herod was a former slave of the Chashmonaim who rebelled against his masters and 
killed all of the Chashmonai family. He pronounced himself king over the Jewish people, along the way killing all the rabbis so they wouldn’t object to a slave becoming king. He spared only one sage, Bava ben Buta, whom he blinded. Then, pretending to be somebody else, he attempted to provoke Bava ben Buta to curse him, but the sage refused. Realizing that killing the rabbis was a mistake, Herod asked Bava ben Buta how he could make amends for what he had done. The sage advised him to build a new and better building for the Beis Hamikdash, which Herod proceeded to do.
Did Herod become a better person by rebuilding the Beis Hamikdash? Highly unlikely, given that he murdered his own wife and sons. But he did make his mark on Yerushalyim – many walls built by Herod are still standing today.
Have a good Shabbos and a meaninful and inspiring Tisha B’Av!