The Prague Gate most probably dates back to the end of the 13th century, when the early medieval fort was replaced by a new system of fortifications. The town walls originally had two gates: the preserved Prague Gate and the Labe (Elbe) Gate, which no longer exists. The first preserved written mention of the Mělník fortifications from the 2nd half of the 14th century refers to this Labe Gate. During its lifetime the Prague Gate underwent several building alterations. The most significant of these was the Renaissance modification from 1536 when one and a half storeys were added on the top. Further reconstructions occurred in 1652 and 1799, when the building caught fire and had to be partially rebuilt. The fortification system gradually fell into disuse during the 19th century and the same fate could have befallen the Prague Gate, which was sold off in 1836 and subsequently used as a water reservoir. The last significant alterations were carried out between 1916 and 1920 according to plans by the architect Kamil Hilbert. At present the building is used as a gallery and tearoom.