The Spalentor is the most imposing of the three surviving city gates that formed part of the fortifications of 1400. When the gate was constructed, it was very important that it had a good overall appearance because it closed off the entrance to Basel from the Alsatians who used to be the most important trading partner of the city. The roof was covered with colourful glazed tiles. Whereas the main middle tower is retangular, the other two towers are round. In the second half of the 15th century, the Spalentor was widened by building another gate in front of it. The gate has two kinds of portcullises which can still be seen today.