Around 1100, a Dutch Count of Zutphen looked at a narrow, easily defended hilltop in the Teutoburg Forest and saw a business model. The trade route from Lübeck through Bremen and Münster to Cologne had to thread this gap - which meant the man at the top could charge for the privilege. The castle that rose here became the seat of the County of Tecklenburg, a small but strategically rich territory whose lords could lean on neighboring Münster and Osnabrück. By 1184 the chroniclers were calling it the mightiest hilltop castle north of the Main. Within a few years, Archbishop Philip of Cologne paid the extraordinary sum of 3,300 marks to acquire the county - a transaction that gave the Archbishops of Cologne the geographical leverage to claim ducal authority over Westphalia itself.

In November 1225, Archbishop Engelbert of Cologne was murdered in a wooded ravine - one of the most shocking political killings of the German Middle Ages, since Engelbert was also regent of the empire. The alleged killer, Frederick of Isenberg, fled to Tecklenburg Castle, where the count harbored him. The papal legate Conrad of Urach responded by laying both castle and town under interdict in 1226. By the following year, Cologne had taken possession of the castle outright. It was the moment Tecklenburg learned the lesson all medium-sized fortresses eventually learn: you can shelter a fugitive once, but the consequences last for centuries.

The Reformation reached Tecklenburg in 1527 under Count Conrad, making the county the first region in Westphalia to convert. After Conrad's defeat at the Battle of Mühlberg in 1547, his daughter Countess Anna inherited a fortress that needed to become a home. She enlarged the windows, built a new entrance road - today's Schlossstrasse - and turned a defensive site into a residence. The bastion her father had thrown up was buried under the new embankment. Countess Anna also did something far more unusual for a 16th-century ruler: she protected those accused of witchcraft. Her court physician was Johann Weyer, the Rhenish doctor whose 1563 book De praestigiis daemonum argued that accused witches were mentally ill, not satanic. In 1884, when the town finally built a memorial tower on the buried bastion, they named it the Wierturm in Weyer's honor - the witches' defender remembered in stone four centuries after his death.

By 1944, the buried bastion had been forgotten so thoroughly that workers digging an air raid shelter rediscovered it by accident, breaking through into a vault no one knew existed. After the war, Tecklenburg found a different use for its ruins. From 1927 onward, plays had been staged in the outer courtyard; in 1949, the Tecklenburg Open-Air Theatre took up permanent residence. Today, 2,300 seats fill the courtyard where Cologne's troops once mustered, and the Mauritz Gate of the 17th century frames a stage equipped for full musical theater. The Wierturm still stands on the inner rampart, brick and round and offering the view that drew the Count of Zutphen here nine centuries ago - a view that turns out to have been worth the cost of building, holding, losing, and finally repurposing an entire castle.