Using P/Invoke and the GetGeoInfo function, you can get some information from a GeoID:

    public static string GetGeoInfo(int geoId, SYSGEOTYPE geoType)
    {
        string s = new string('\0', 256);
        int size = GetGeoInfo(geoId, geoType, s, 256, 0);
        if (size <= 0)
            return null;

        return s.Substring(0, size - 1);
    }

    public enum SYSGEOTYPE
    {
        GEO_NATION = 0x0001,
        GEO_LATITUDE = 0x0002,
        GEO_LONGITUDE = 0x0003,
        GEO_ISO2 = 0x0004,
        GEO_ISO3 = 0x0005,
        GEO_RFC1766 = 0x0006,
        GEO_LCID = 0x0007,
        GEO_FRIENDLYNAME = 0x0008,
        GEO_OFFICIALNAME = 0x0009,
        GEO_TIMEZONES = 0x000A,
        GEO_OFFICIALLANGUAGES = 0x000B
    }

    [DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)]
    private extern static int GetGeoInfo(int geoId, SYSGEOTYPE geoType, string lpGeoData, int cchData, int language);

But, beware, you may not have a 1:1 correspondence between a Geographic location and a Region.