The Holsten Gate ("Holstein Tor", later "Holstentor") is a city gate marking off the western boundary of the old center of the Hanseatic city of Lübeck. Built in 1464, the Brick Gothic construction is one of the relics of Lübeck's medieval city fortifications and one of two remaining city gates, the other being the Citadel Gate ("Burgtor"). Known for its two-round towers and arched entrance, it is regarded today as a symbol of the city. Together with the old city centre (Altstadt) of Lübeck it has been a UNESCO World Heritage Site since 1987. The Holsten Gate is composed of a south tower, a north tower and a central building. It has four floors, except for the ground floor of the central block, where the gate's passageway is located. The side facing west (away from the city) is called the "field side", the side facing the city the "city side". The two towers and the central block appear as one construction when viewed from the city side. On the field side, the three units can be clearly differentiated. Here the two towers form semicircles which at their widest point extend 3.5 metres beyond the central block. The towers have conical roofs; the central block has a pediment. The rich and wealthy Hanseatic city of Lübeck felt the need in the course of the centuries to protect itself from outside threats with ever stronger walls and fortifications. Three gates gave access to the city: the Citadel Gate in the north, Mill Gate in the south, and the Holsten Gate in the west. To the east, the city was protected by the dammed Wakenitz River. Here, the less martial Hüxter Gate led out of the city. These city gates were initially simple gates which were repeatedly strengthened over time so that they eventually all had an outer, middle and inner gate. Today, only fragments remain of these ancient city gates. The gate now known as the Citadel Gate is the former Interior Citadel Gate; the Middle and Outer Citadel Gates no longer exist. All three Mill Gates have completely disappeared. The gate now known as the Holsten Gate is the former Middle Holsten Gate; there was also an (older) Inner Holsten Gate, an Outer Holsten Gate, and even a fourth gate, known as the Second Outer Holsten Gate. So the history of the Holsten Gate is actually the history of four consecutive gates, although only one of them is left. The names of the individual gates changed as a matter of course as their components emerged and disappeared. The Middle Holsten Gate was once the Outer Holsten Gate before the gates on either side were constructed. Still today there is a great deal of confusion about the names as one studies the historical record.