Torretrencada is a Talayotic settlement (1000-700 BCE) that was occupied until the Roman conquest in 123 BCE. Several of its monuments can still be seen. They include the talayot a seriest of artificial burial caves dug out of the rocky ground and burial chambers carved in the rock, probably dating from the high medieval period. The taula is one of the most beautiful on the island, with a reinforcement pillar at the back, but all that is left of the surrounding wall is a section underneath the modern dry-stone wall. The site dates back to the post-Talayotic period (650-123 BCE) and was used by the community for performing rituals.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.