The 100 steps denote 100 keywords, which most characterise the period of 1870–1992. These may be building types, or so much as fields (railway architecture, the municipal building, the rural schoolhouse, the private dwelling), specific structures (the Riigikogu building, TV- and radio buildings, the Munamäe viewing platform, the Seaplane Hangars, etc.), types of settlements (the micro-district, the rural settlement, the hamlet, the summer-home cooperative, etc.), architects (Karl Burman, Edgar Velbri, Raine Karp, Toomas Rein, etc.), building materials (silica brick, reinforced concrete, large block, etc.), or styles (historicism, functionalism, art-nouveau, Stalinism, etc.). This allows all more significant architectural phenomena in 20th-century Estonian architecture to be covered: both crowning achievements and everyday architecture. Both less-known buildings and those not protected as items of cultural value so far are presented, as are structures that are already under state protection.