keystone/api-ref/source/v3/samples/admin/region-create-response.json

{
    "region": {
        "parent_region_id": "RegionOne",
        "id": "RegionOneSubRegion",
        "links": {
            "self": "http://example.com/identity/v3/regions/RegionOneSubRegion"
        },
        "description": "My subregion"
    }
}