Maria im Spiegel (Sion Convent), Cologne

In medieval times the site mostly belonged to religious institutions or the city's patrician elite. Daughters of these often intermarried families founded or entered convents, and thanks to their social standing, education, and dowries, they quickly rose to leading positions. As prioresses or abbesses, they used family connections to secular and ecclesiastical offices to increase their communities' wealth.

In 1229 the Cologne patrician Gerhard Quatermart granted the Franciscans (Minorites) a plot in the parish of St. Severin, near the Katharinengraben in the "Sion Valley," for an oratory—their first permanent settlement since arriving in Cologne in 1222. Around 1245 they sold the property to Count Heinrich von Sayn and moved to the St. Kolumba parish, where they began building the Minorite Church.

Heinrich von Sayn (died 1246) and his wife Mechthild, née von Landsberg, transferred the former Minorite property to a Cistercian community that called itself "Maria im Spiegel" (de Speculo S. Mariae). The endowment stipulated that Mechthild would retain use of part of the garden and buildings, with the remainder passing to the convent only once there was no heir. Pope Innocent placed the convent under his protection in 1247, and in 1248 charged the Cistercian order's leadership with incorporating it under the oversight of the Abbot of Heisterbach.

The name "Maria im Spiegel" (de Speculo S. Mariae) may derive from the Cologne patrician family "von Spiegel," from which the foundress came. After the Sayn founders, popular usage named the institution Sion Convent or Seyne; in Hermann von Weinsberg's time it was called the "Jungfernkloster zu Seien." In 1283 Countess Mechthild (died 12 November 1285) endowed the convent again, referring to "van mine Cloister ze Colne"; she was buried beneath the high altar she had donated to the convent church. Further endowments followed from Cuno von Horne in 1280 and Werner Overstolz in 1331.

The church was built during a period of intense 13th-century construction, when numerous churches and monastic complexes were erected across Cologne. Whether it reached its later size already under the brief Franciscan tenure or only under Countess Mechthild remains unknown.

Several surviving streets recall the convent and its founders: Seyengasse, Sionstal, and the Landsberg- and Mechtildisstraße, named after Mechthild. The former "Bozengasse" became today's Buschgasse.