The Roman theatre in Vienne was built around 40-50 AD and is considered to be one of the largest theatres in Roman Antiquity with a capacity of 11500 seats and a diameter of 130 metres. In the 2nd century it was double sized by a second smaller theater, the odeon, which was built nearby on the southern slope of the ravine of Saint-Marcel.
The annual Vienne Jazz Festival has been held on the ancient theatre since 1980.
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.