Besides the graves, mausoleums and other curiosities, one of the church's major attractions are its stained glass windows.The New Church's stained glass windows fall into two general categories: the windows with Biblical themes, and memorial windows such as the Prince William window and Wilhelmina window. The latter commemorate important events or people in Dutch history.The New Church was filled with brightly coloured stained glass windows as far back as the Middle Ages. But after the city fire of 1536 and the Delft Thunderclap (gunpowder explosion) of 1654, nothing remained of them. It was only in the 20th century that the church was fitted with a new collection, with most of them made by Willem Adriaan van Konijnenburg.