Analysis has demonstrated that they were his personal tubs, the team writes. Why did Herod have bathtubs, anyway? Because he sought to introduce Roman cultural norms to Judea, including Roman bathing culture, a habit recently demonstrated to have led the ancient Romans to share not only bathwater, but also parasites.
It bears adding that all along, archaeologists have assumed that while fine alabaster projects were made of Egyptian stone, it was clearer that poorer quality vessels around the Levant were made of local gypsum. Herod would not have abided tacky materials in his great works, as Josephus says regarding the temple project: “…as esteeming it to be the most glorious of all his actions, as it really was, to bring it to perfection; and that this would be sufficient for an everlasting memorial of him,” which explains a great deal.