Zwolle once had a full set of medieval city gates. The Sassenpoort, the Saxon Gate, is the only one that survived into the present. Its name points east, toward the Saxon-speaking lands beyond the city, where the road through this gate led. It was built in 1409 from dimension stone hauled in for the purpose, mostly trachyte and tuff. Both are volcanic rocks quarried in the Eifel hills of Germany and shipped down the Rhine and IJssel, a luxury choice that signaled wealth. More than a century earlier, in 1294, Zwolle had joined the Hanseatic League, the trading confederation that ran the medieval North Sea and Baltic economy. A heavy gate in expensive imported stone was a way of announcing arrival.

Between the gate's two corner towers runs a projecting platform called a machicolation, a defensive feature with openings in the floor through which defenders could drop heavy or burning things on whoever stood below. Whether anyone ever actually poured boiling oil here is unrecorded, but the architecture made the threat credible. By the 1890s the threat was long gone and the building was beginning to look its age. Between 1893 and 1898 the city restored it heavily, fitting dormers into the roof and replacing the 18th-century spire with a new Neo-Gothic clock tower. That spire still rises above central Zwolle today. Most photographs of the gate frame it as a single object, but in person the tower's vertical lift is the first thing you notice.

In 1893, at the start of that restoration, the city handed the gate over to the Dutch national government, which used it for many years as a storage depot for the national archives. The state still owns it. On 13 February 1967 the building was declared a rijksmonument, one of the country's official protected monuments, and it sits in the elite Top 100 of Dutch heritage sites. The classification places it in category I, reserved for monuments considered of extraordinary historical importance. In 2010, to stop exhaust fumes from eating away at the stone, traffic was banned from passing under the arch. Today the gate functions as a pedestrian thoroughfare, walked through daily by people who likely register the medieval mass above their heads only in passing.

The thirteen surviving coats of arms read like an index of the medieval Overijssel polity. Delden, Deventer, Enschede, Genemuiden, Hasselt, Kampen, Oldenzaal, Ootmarsum, Steenwijk, Vollenhove, and Zwolle itself, along with the arms of the Netherlands and of Overijssel province. They are the towns that mattered, and the powers above them. The missing fourteenth, the knighthood's arms, would have completed a kind of constitutional portrait of late-medieval Overijssel. In 2006 the Dutch post office TPG Post issued a stamp in its Mooi Nederland series featuring the gate, a small modern endorsement of what is by some distance the most photographed silhouette in central Zwolle.