Complex sentence: At southwest end of the village of Haby the meadows are filled with fog some nights where once til the mid of last century was a big lake which was linked to the Wittensee.
Split into simpler sentences: At southwest end of the village of Haby the meadows are filled with fog some nights. This is where there was, until the middle of the last century, a big lake which was linked to the Wittensee.