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The Delft town fire of 1536 and the turmoil of the Protestant Reformation brought a premature end to an ambitious expansion project led by two members of the Keldermans family of master builders. This construction phase resulted in the flat-roofed, stone-walled northern transept arm that differs markedly in style from the older parts.
The great fire, iconoclasm, weather, and the explosion of the town’s gunpowder store in 1654 (see Delft Explosion) took their toll on the church and its furnishings, necessitating much repair work over the years. During one renovation, the tower turrets were rebuilt in a more vertical alignment than the leaning body below, giving the tower as a whole a slightly kinked appearance. The current stained-glass windows were crafted by the master glazier Joep Nicolas in the mid-20th century.
The church possesses three pipe organs, from the years 1857 (main organ), 1873 (north aisle) and 1770 (choir).
The most massive bell in the tower, cast in 1570 and called Trinitasklok or Bourdon, weighs nearly nine tonnes, and because of its strong and potentially damaging vibrations, is rung only on such special occasions as the burial of a Dutch royal family member in the nearby New Church. The massive bell is also sounded during disasters, when local air-raid sirens are sounded. This, however, does not happen during the siren’s monthly, country-wide test, which happens every first Monday of the month.

The New Church, formerly the church of St. Ursula (14th century), is the burial place of the princes of Orange. It is remarkable for its fine tower and chime of bells, and contains the splendid allegorical monument of William the Silent, executed by Hendrik de Keyser and his son Pieter about 1621, and the tomb of Hugo Grotius, born in Delft in 1583, whose statue, erected in 1886, stands in the market-place outside the church.[1] The tower was built 1396-1496 by Jacob van der Borch, who also built the Dom in Utrecht during the years 1444-1475. The monument for Hugo de Groot was made in 1781. The mechanical clock has 18 bells by Francois Hemony from 1659 and 30 modern bells. In the church tower there is a bell from 1662 by Francois Hemony with a diameter of 104 centimeters. In the tower there are also bells no longer in use, including 13 from 1659 by Francois Hemony, 3 from 1678 by Pieter Hemony, 3 from 1750 from Joris de Mery, and 1 from Gillett and Johnston from 1929. Don’t forget to climb the tower. On fair days you will have a stunning view over historical Delft and her surroundings.