In the first sentence Switzerland is used as an adveb of place, but in the second sentence Seoul is used as a subject. Let me explain by changing your sentences:
Originally Posted by bombo109
Switzerland has a very low rate of unemployment. Salaries are twice the European average in this country.General tips to understand the structure:
Seoul is the capital of South Korea. This country has a population of 10 million.
1- Where cannot be used before a main verb, while which can.
2- Try to put the noun which is modified into the relative clause. If it takes in/on or at preposition in front of itself, you need a "WHERE" or "prep + which" as a relative adverb.