The Roquefavour Aqueduct in Ventabren, near Aix-en-Provence, was first planned in 1565, but it was not realized until the 19th century. It was designed by Jean François Mayor de Montricher, built between 1841 and 1847, and is the largest stone aqueduct in the world. It took 5,000 labourers, including 300 stone-cutters, and it cost 3,800,000 French francs. It is 83 metres high, 375 metres long, and the foundations are 9 to 10 metres deep.
The aqueduct brings water (Canal de Marseille) from the Durance river to the Palais Longchamp in Marseille, all the way to La Ciotat.
References:Celje Castle was once the largest fortification on Slovenian territory. The first fortified building on the site (a Romanesque palace) was built in the first half of the 13th century by the Counts of Heunburg from Carinthia on the stony outcrop on the western side of the ridge where the castle stands. It had five sides, or four plus the southern side, which was a natural defence. The first written records of the castle date back to between 1125 and 1137; it was probably built by Count Gunter. In the western section of the castle, there was a building with several floors. Remains of the walls of this palatium have survived. In the eastern section, there was an enclosed courtyard with large water reservoirs. The eastern wall, which protects the castle from its most exposed side, was around three metres thicker than the rest of the curtain wall. The wall was topped with a parapet and protected walkway.