Wikipedia:WikiProject Geographical coordinates/region:

The region: parameter specifies the political region for terrestrial coordinates. It is used to select appropriate map resources. If no region: parameter is provided, GeoHack attempts to determine the region from the coordinates.

The region should be supplied as either a two character ISO 3166-1 alpha-2 country code or an ISO 3166-2 region code.

Examples of ISO 3166-1 alpha-2 codes:

• AQ Antarctica
• AU Australia
• BR Brazil
• DE Germany
• GB United Kingdom
• HK Hong Kong
• IN India
• LK Sri Lanka
• RU Russia
• US United States

Examples of ISO 3166-2 region codes:

• DE-TH Thuringia, Germany
• GB-BIR Birmingham, England
• NO-03 Oslo, Norway
• US-NY New York state, US

The oceans have the following Wiki assigned code elements per de:Vorlage:Coordinate#Ozeane.

• XN Arctic Ocean
• XA Atlantic Ocean
• XI Indian Ocean
• XP Pacific Ocean
• XS Southern Ocean

In addition, two Wiki assigned code elements can be used with {{coord}}:

• XZ for objects in or above international waters (similar to UN/LOCODE).
• ZZ for use in examples.

Samples

Focus region	Region	Markup	Result
Switzerland	CH	{{coord|46.9524|N|7.4396|E|region:CH}}	46.9524°N 7.4396°E / 46.9524; 7.4396
Berlin, Germany	DE-BE	{{coord|52.5164|N|13.3775|E|region:DE-BE}}	52.5164°N 13.3775°E / 52.5164; 13.3775