Almost nothing remains of Northampton Castle, which was one of the most important royal castles in medieval England — it hosted parliaments, served as a prison, and was the site of Thomas Becket's trial before Henry II. The Victorians demolished the majority of it in 1879 to build the railway station that now occupies the site.
A postern gate survives, incorporated into the railway station wall along Chalk Lane. A small interpretive display near the station explains the castle's history and significance. The sheer scale of what was lost — a major royal fortress that shaped English history — makes this absence worth understanding. For those interested in what the castle would have looked like, Rockingham Castle (25 kilometres north) survives as a comparable medieval fortification.