The single most surprising building in Hitchin: a sprawling 14th- and 15th-century Perpendicular Gothic parish church that dwarfs the small town it stands in. The flint-and-stone exterior is broad and low; inside, the wooden ceiling is intricately carved, the misericords below the choir stalls are decorated with green men and dragons, and there is a fine 15th-century stone screen across the chancel.
A short walk down a paved lane from the Market Place, the church sits beside the river Hiz and is normally open daytime. Free; donations welcome. The tower can sometimes be climbed on open days.