Here is the full list of all 12 Travel Riddles: Trip To Greece achievements.
Match 6 pieces in one combination
Complete the first tutorial level
Match 5 pieces in one combination
Match 4 pieces in one combination
Complete all levels in the Athens Episode
Complete all levels in the Santorini Episode
Complete all levels in the Crete Episode
Complete all levels in the Sparta Episode
Complete all levels in the Olympia Episode
Complete all levels in the Delphi Episode
Complete all levels in the Meteores Episode
Complete all levels in Village Episode