I'm looking for a word which can be used to describe a location upon the earth which does not belong to a country. For example 'North America' though the word 'continent' can be used here. Another example would be the 'Mid-Atlantic Ridge'.
Words like 'location' or 'toponym' are not specific enough and could equally be used to describe somewhere within a country.
Within a sentence I would use it something like:
"The Mid-Atlantic ridge doesn't belong to a country, so it is (countryless)"