Why is the first floor of most Czech buildings actually the second floor?

For most Brits and Europeans, the Czech floor numbering system is standard – the first floor above the ground is known as the ground floor (přízemi) while the next floor up is the first floor (known alternatively as the první patro or první poschodí – poschodí means by the stairs). Americans (as well as Japanese and Russians), however, may be confused because they tend to use the term first floor to refer the first floor above the ground. To confuse matters, the Czech word podlaží can be used in the American sense of numbering so that 1. patro = 2. podlaží.