In order to understand how to design an underground space, I looked at three case studies.
Derinkuyu is the biggest out of several underground cities found in Turkey. Christians built the city for protection during the Arab-Byzantine wars (780-1180). The city was capable of housing 20 000 people, complete with chapels, schools, stables and food storage. The lowest levels accessed ground water. The city was last used as a shelter in the early 20th century. The entrance could be closed from the inside with large stone doors. Every floor can be closed off the same way, so inhabitants can see further underground if need be.
Located just outside Krakow, Poland, the salt mines has for centuries been one of Poland’s main sources of income. It opened in the 13th century and has been exponentially growing until the 20th century. Mining ended in 1996 due to lowered salt prices and problems with flooding. Now the mine is one of Poland’s most visited tourist attractions with about 1.2 million visitors annually. Due to its scale and depth, miners spent most of their life underground. The horses used for the mining never say the light of day. The miners built a cathedral and several smaller chapels inside the mine.
Located at the intersection of Oxford Street and Regent street, Oxford Circus is the busiest rapid-transit station in London with 98.51 million entries and exits in 2014. The whole station is underground. The entrances are staircases leading straight down from the street.
It First opened in 1900 and has been rebuilt several times, latest being the addition of the Victoria line in 1969. The station is designed to move as many people quickly and easily to their destinations.
The Bakerloo and Victoria lines are separated from Central line, but there are various shortcuts between the two sections for transit passengers and people who took a wrong turn.