The Bochnia Salt Mine is one of the oldest salt mines in the world and the oldest one in Poland. The mine was established between the 12th and 13th centuries after salt was first discovered in Bochnia, and became part of the Royal mining company żupy krakowskie (Kraków salt works).
The mine was closed some time after World War I. In 1981 it was declared a heritage monument. The site is one of Poland's official national Historic Monuments, as designated October 6, 2000, and tracked by the National Heritage Board of Poland.
The mine shafts measure 4.5 kilometres in length at about 330–468 metres in depth below the surface, at 16 different levels. The August Passage is the main communication and transportation route in the mine. It runs from the east to the west of mine, connecting in a straight line the bottom ends of the Campi and Sutoris shafts. It is situated at a depth of 176m - from the top of the Sutoris shaft and the depth of 212m counting from the top of the Campi shaft. The August Passage was initially called the Long Stove. Its first part, extending between the Rabsztyn Chute and a Campi Shaft was built in the years 1723-1743, in accordance with a design by Jan Gottfried borlach. His great achievements was to regulate routes in the mine by ensuring their straightening and leveling. As a result of this, over the next decades, the August Passage was able to reach a length of nearly 3-km. Excavated chambers, shafts and passages form an underground town, which is now open to sightseers. The largest of the preserved chambers has been converted into a sanatorium.
The Ważyn Chamber was named after the name of the administrator Andrzej Ważyński. The deepness of this chamber, the biggest in Bochnia Salt Mine, is 248m, its length - 255m, its maximum width 14,4m and maximum height 7,2m. The chamber uses no supporting pillars. Salt from Ważyn chamber was extracted from 1697 until the 1950s.
In 2013 the mine was added to the UNESCO World Heritage List as an extension of the Wieliczka Salt Mine inscription of 1978.
References:The city walls of Avila were built in the 11th century to protect the citizens from the Moors. They have been well maintained throughout the centuries and are now a major tourist attraction as well as a UNESCO World Heritage Site. Visitors can walk around about half of the length of the walls.
The layout of the city is an even quadrilateral with a perimeter of 2,516 m. Its walls, which consist in part of stones already used in earlier constructions, have an average thickness of 3 m. Access to the city is afforded by nine gates of different periods; twin 20 m high towers, linked by a semi-circular arch, flank the oldest ones, Puerta de San Vicente and Puerta del Alcázar.