Besides the well-known Egyptian Pyramids and Roman aqueducts, one interesting one I've recently learned about was about the columns in the Roman Pantheon were built: They were carved from single blocks of granite and then imported all the way from Egypt[0]:

"The grey granite columns that were actually used in the Pantheon's pronaos were quarried in Egypt at Mons Claudianus in the eastern mountains. Each was 39 feet (11.9 m) tall, 5 feet (1.5 m) in diameter, and 60 tons in weight.[43] These were dragged more than 100 km (62 miles) from the quarry to the river on wooden sledges. They were floated by barge down the Nile River when the water level was high during the spring floods, and then transferred to vessels to cross the Mediterranean Sea to the Roman port of Ostia. There, they were transferred back onto barges and pulled up the Tiber River to Rome.[44] After being unloaded near the Mausoleum of Augustus, the site of the Pantheon was still about 700 meters away.[45] Thus, it was necessary to either drag them or to move them on rollers to the construction site."

0. https://en.wikipedia.org/wiki/Pantheon,_Rome#Portico