I wasn't sure if there had ever been a monastery at the site of my fictional town which is a real town in real life so I had to be cautious and when I had the chance I checked the details.
My fictional St. Gabriel's monastery was built about 1000 AD, made of wood. That way when it fell into ruin sometime after 1307 AD there would be no trace of it in the modern world as there would be from a stone one. Plus timber (a wattle and daub structure) would more easily burn if I needed it to.
I imagined in the Eastern Arcade salt and grain would be stored at the near end of the promenade.
The time in Switzerland proved to be necessary. I discovered that a monastery does dominate the town of Altdorf. It has been there since the 1580's. In the book I had Stefan wonder if there'd ever been one, so I had to make a quick adjustment during the final edit, to counteract that major error. While in Switzerland, I found it fascinating to discover here is little difference from the Uri Bull emblem seen in Altdorf today and the one common in 1315 AD.