Map of the city of Leiden, Dutch Republic, 1600, by Pieter Bast. Netherlands
I'm working on a synthesis of Leiden's city defensive works from the Medieval and Early Modern periods and how those were developed throughout the city's history. Comparing several contemporary city maps gives a solid basis for the research, along with archaeological finds and historical records such as financial accounts (defensive works are expensive!).
This is one of my favourite maps because of its colours and because it shows the city medieval city walls in a transitional period, before the city expanded further outwards. You'll notice three bastions that were added quickly after the sieges of 1573-1574. If you look at all the towers along the wall you'll notice that most of them are short and have no roof. Originally those were the same as towers with roofs, but they were 'decapitated' in the 16th century. They were too vulnerable to artillery fire, meaning they would collapse and would become useless. If they collapsed into the moat, those spots could even become scalable.
At this time the backs of the medieval city walls were filled with earth to withstand artillery fire. Most of Leiden's medieval city walls had been curtain walls; so no parapets or battlements existed along the walls before this period.