This church was built between 1185 and 1325 as a colegiate church.
The first years, it was situated outside the town, but soon incorparated.
Since
Lippstadt is a town surrounded by the Lippe river and various canals ('Venice of Westphalia'), in some parts the ground really was (is) wet. Like around that church.
So it couldn't been used since the late 18th, early 19th century and people just let it become a ruin.
In 1847, some people fortunately remembered from own eyesight how it looked alike origianally: