[BenLurkin]

Something I’ve always wondered was how the Romans got water to flow uphill in their aqueducts. Siphon effect, maybe?

[Larry Lucido]

Possibly. From AI overview:

Using siphons for valleys:
.
When an aqueduct needed to cross a valley, they sometimes used siphons. These involved a steep plunge down one side of the valley and a steep climb up the other, utilizing water pressure to bring it back up to the original height.

[SunkenCiv]

Yup, they sometimes built a siphon in their aqueducts.

[cpdiii]

Something I’ve always wondered was how the Romans got water to flow uphill in their aqueducts. Siphon effect, maybe?

They did not. Thus the purpose of the aqueduct bridges to take the water across valleys. Everything was downhill. They were excellent engineers.