Steinerne Brücke in Regensburg is a 12th-century bridge across the Danube linking the Old Town with Stadtamhof. For more than 800 years, until the 1930s, it was the city's only bridge across the river. It is a masterwork of medieval construction and an emblem of the city.
Charlemagne had a wooden bridge built at Regensburg, approximately 100 metres east of the present bridge, but it was inadequate for the traffic and vulnerable to floods, so it was decided to replace it with a stone bridge. The Stone Bridge was built in only eleven years, probably in 1135–46. Louis VII of France and his army used it to cross the Danube on their way to the Second Crusade. It served as a model for other stone bridges built in Europe in the 12th and 13th centuries. For centuries it was the only bridge over the river between Ulm and Vienna, making Regensburg into a major centre of trade and government.
The Stone Bridge is an arch bridge with 16 arches. At the south end, the first arch and first pier were incorporated into the Regensburg Salt Store when it was built in 1616–20, but remain in place under the approach road to the bridge. An archaeological investigation was performed in 2009, and revealed fire damage during the Middle Ages.References:
Derbent is the southernmost city in Russia, occupying the narrow gateway between the Caspian Sea and the Caucasus Mountains connecting the Eurasian steppes to the north and the Iranian Plateau to the south. Derbent claims to be the oldest city in Russia with historical documentation dating to the 8th century BCE. Due to its strategic location, over the course of history, the city changed ownership many times, particularly among the Persian, Arab, Mongol, Timurid, Shirvan and Iranian kingdoms.
Derbent has archaeological structures over 5,000 years old. As a result of this geographic peculiarity, the city developed between two walls, stretching from the mountains to the sea. These fortifications were continuously employed for a millennium and a half, longer than any other extant fortress in the world.
A traditionally and historically Iranian city, the first intensive settlement in the Derbent area dates from the 8th century BC. The site was intermittently controlled by the Persian monarchs, starting from the 6th century BC. Until the 4th century AD, it was part of Caucasian Albania which was a satrap of the Achaemenid Persian Empire. In the 5th century Derbent functioned as a border fortress and the seat of Sassanid Persians. Because of its strategic position on the northern branch of the Silk Route, the fortress was contested by the Khazars in the course of the Khazar-Arab Wars. In 654, Derbent was captured by the Arabs.
The Sassanid fortress does not exist any more, as the famous Derbent fortress as it stands today was built from the 12th century onward. Derbent became a strong military outpost and harbour of the Sassanid empire. During the 5th and 6th centuries, Derbent also became an important center for spreading the Christian faith in the Caucasus.
The site continued to be of great strategic importance until the 19th century. Today the fortifications consist of two parallel defence walls and Naryn-Kala Citadel. The walls are 3.6km long, stretching from the sea up to the mountains. They were built from stone and had 73 defence towers. 9 out of the 14 original gates remain.
In Naryn-Kala Citadel most of the old buildings, including a palace and a church, are now in ruins. It also holds baths and one of the oldest mosques in the former USSR.
In 2003, UNESCO included the old part of Derbent with traditional buildings in the World Heritage List.