The Fortino di Mazzallakkar is a ruined Arab fort in Sambuca di Sicilia. It is located near Lago Arancio, and is partially submerged by its waters for six months of every year.
The Fortino di Mazzallakkar was built by the Arabs in around 830 AD, possibly to defend the territory around Sambuca di Sicilia, which was then known as Zabut.
The fort was still in good condition until the mid-20th century, and it was used as a shelter for sheep and cattle. In the 1950s, the Carboj dam was built, causing the flooding of Lago Arancio. The fort is located at the edge of the lake, and is partially submerged around 6 months of the year. This has caused a lot of damage to the fort.
The fort is privately owned, and can be visited on request.
References:
The Petersberg Citadel is one of the largest extant early-modern citadels in Europe and covers the whole north-western part of the Erfurt city centre. It was built after 1665 on Petersberg hill and was in military use until 1963. It dates from a time when Erfurt was ruled by the Electors of Mainz and is a unique example of the European style of fortress construction. Beneath the citadel is an underground maze of passageways that can be visited on guided tours organised by Erfurt Tourist Office.
The citadel was originally built on the site of a medieval Benedictine Monastery and the earliest parts of the complex date from the 12th century. Erfurt has also been ruled by Sweden, Prussia, Napoleon, the German Empire, the Nazis, and post-World War II Soviet occupying forces, and it was part of the German Democratic Republic (East Germany). All of these regimes used Petersberg Citadel and had an influence on its development. The baroque fortress was in military use until 1963. Since German reunification in 1990, the citadel has undergone significant restoration and it is now open to the public as a historic site.