In the Americas, there is La Danta Temple (built c300 BC, 230 ft / 70.10m) in modern-day Guatemala. In Asia (Far East and South Asia), there is the Ruwanwelisaya (built c300 BC, 300 ft / 91.44m) in Sri Lanka. What is there in Europe?
The Wikipedia page History of the world's tallest buildings makes no mention of anything between the Great Pyramids and Lincoln Cathedral (1300). The List of Greek and Roman architectural records doesn't come up with anything more than the Pont du Gard at 160 ft / 48.77m (or 155 ft / 47.24m, depending on which Wiki article you believe). The Colosseum is another possible candidate at 157 ft / 47.85m (or 159 ft / 48.46m according to The Colosseum.net)
The Pont du Gard and the Colosseum.
To clarify, by 'ancient times' I mean any time up to the fall of the Western Roman Empire. However, I'd also be interested in anything taller than the examples above which was built before 1000 AD i.e. Early Medieval.
I'm only interested in man-made structures which are still standing, even if not in their entirety.