Spiral stairs are very old, almost as old as architecture itself. They were used already in medieval times in castles. Then they were twining clockwise, so that there would be a disadvantage for right-handed attackers. First spiral stairs were made of stone slabs mounted to the wall.
Spiral stairs were mostly used outdoors or in commercial applications, where they provided access to skywalks in factories or storage areas in warehouses. Their most important place was in lighthouses where no other type of stairs was an option.
Nowadays, spiral stairs are still used because of the small amount of space that they require. They are great space savers with outdoor applications as fire escapes and indoors for climbing to lofts and libraries. The appearance is beautiful and creates romantic atmosphere. This type of stairs definitely need a railing because it might be too dangerous without it (naturally it also depends on the height of the stairs).
You can choose between several materials but most popular are still metal and wood. It is recommended to use metal when building spiral stairs outdoors.
If you're confident in your carpentry, you can go online to buy detailed plans for hammering together a spiral in your workshop, otherwise it is recommended to use handymen who would come and help you to build the staircase that you have always dreamed of.