in the city's east wall at the end of Vlamingstraat in the long stretch between the Haagpoort and the Oostpoort.

The Koepoort was at the end of Vlamingstraat in the long stretch between the Haagpoort and the Oostpoort. It is first mentioned in Delft's Archief Kerkvoogdij (Ecclesiastical Archive) in 1400. It is also the smallest of the old gates, although not much smaller than the Schoolpoort.

Like the Schoolpoort, the Koepoort did not lead to a canal that led to other cities, as did other gates. The land gate over the drawbridge was used for getting the cows (koe = cow) to the market. Most of them came from the nearby meadows. Some came from as far away as Denmark. Though the long walk without enough food left them in poor health, they were still profitable. Compared to the major gates, the Koepoort had the reputation in Leeuwenhoek's time as unpretentious even insignificant (onaanzienlijk: Bleyswijck, 1667) and small and poor (geringe and slechte: Boitet, 1729)

Blaeu's 1649 Delft Batavorum map (right) shows a small round tower to the south of the bridge where the gracht meets the singel. on the Kaart Figuratief, made thirty years later, the round tower is gone and a small house tops the land gate, owned by the city. This house was more for the gatekeeper who raised and lowered the drawbridge than it was for military defense. From 1694 to her death in 1733, the gatekeeper was Maria van der Hiel, wife of surgeon Johannes de Kets.

The Koepoort also had a water gate. Given the location away from the Vliet and Schie canals, boats could get to it only by passing under the Oostpoort and Rotterdamse Poort bridges from the sourth or the Haagpoort bridge from the north. The water gate had a lattice fence that was lowered at night just as the land gate was locked each night. As shown in the images (left sidebar), it was too low for boats with masts and sails to pass under.

Many images of the Koepoort show a tall building next to it. On the Kaart Figuratief of 1678 (right), it is just to the north of the bridge, with the label Drogerie. The building was the city drying shed (stadsdrogerij), used in rainy weather for keeping dry sheets of fabric of the kind Leeuwenhoek sold in his store.

In March 1861, the Delft city council gave permission to demolish the Koepoort and fill in the water gate to make room for new houses from the Rietveld past Vlamingstraat. The current bridge by that name was constructed in the mid-20th century at the end of Nieuwe Langendijk about a hundred yards to the south of the original.

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