How did Herod make his temple complex larger than Solomon's?
Herod enlarged the temple complex by investing great work and expense, building massive retaining walls and filling in the area to expand the mountain on which Solomon's temple had stood. That artificial enlargement made Herod's complex much larger than Solomon's, with the fill carefully kept ceremonially undefiled.
Les explains that Herod put a lot of work and expense into the project. He built great retaining walls and filled in the area to enlarge the mountain on which Solomon's temple had stood, so Herod's complex ended up much larger than Solomon's. Les also shares a guide's insight: when Herod built the extension on the mountain, the fill had to be “kosher fill.” They made sure the fill dirt contained nothing that would defile it—no corpses, bones, or anything like that—so it was undefiled dirt. The temple itself was beautiful and gorgeous, but Herod's additions expanded the site far beyond Solomon's original temple mount.