The base of the tower is brick with a tuff cladding on the outside, decorated with shallow Lombard bands that mark its Romanesque ancestry. Built around 1225, it stands 16.5 meters before the brick extension added when the Gothic nave reached 24 meters and demanded a taller companion. The original gable roof was replaced in 1611 by the spire that still crowns the town today. Inside, the oldest object is older still: a baptismal font hewn from a single piece of Bentheimer sandstone, carved with grapevines that quote the Gospel of John - I am the vine, thou art the branches. The font drifted out of the church at some point and spent years standing in a city park, until the city archivist F.A. Hoefer brought it home around 1900. In 1959 it returned to its proper place in front of the pulpit, eight hundred years of use and exile finally settled.

The choice the builders of Hattem made in the early 1400s tells you something about ambition and budget. The big churches at Zwolle and Deventer rose as hall churches, broad and high with side aisles the same height as the nave. The smaller northern Veluwe towns - Harderwijk, Elburg, Hattem - opted instead for the basilical plan, looking south toward St. Martin's Cathedral in Utrecht and the Bovenkerk in Kampen for their model. A basilical church has a tall central nave and lower aisles flanking it, the wall above the arcade rising through a triforium and a clerestory. It is the older Roman idea, simpler to engineer, easier to light. In Hattem the form is kept pure. The Black Death was sweeping Europe while this was being built, and the choir was consecrated to St. Andrew and St. Catherine of Alexandria on 27 October 1407 - a deliberate naming for the town that had taken its city rights only a century before.

In 1429 lightning struck the new church. The fire it started forced restoration that lasted years; the altars were rededicated only on 11 June 1436. Expansion continued into the next century, with the Annakapel added on the north side around 1504 and the Mariakapel on the south completed around 1440. Then the Reformation came. The Catholic side altars were demolished, the magistrate of Hattem and his aldermen installed their family pews where saints had stood, and a choir screen and pulpit went up in the 1640s to mark the new Protestant order. Yet the church kept its bones. The painted decoration - fantasy flowers, rushes, rosettes - lay quietly under whitewash for centuries until restorers brought it back during the long interior renovation of 1986 to 1995. Even the wooden pews that once seated Hattem's leading families survive, restored to their original color.

The church holds two pipe organs of very different temperaments - one literal, one figurative. The older Slegel organ traces its core to the middle of the 1500s; the case was reworked and the pipework completed by Jan Slegel in 1677. The Flentrop firm restored it in 1974, aiming to recover the 1677 sound. It still tunes to meantone temperament - the tuning system of the Baroque, where some intervals ring almost too pure and others snarl, a reminder that equal temperament was a 19th-century compromise we have largely forgotten was a compromise. The large organ standing across from it has a stranger origin: its case was originally built in 1855 by Francois-Bernard Loret for a church in Waterloo, Belgium. When it came empty to Hattem in 1974, Flentrop rebuilt it with new pipework and accents of gold leaf. Two centuries, two countries, two tunings - and on Sunday morning, the same congregation.