Simplify the following text for a Grade 9 native English-speaking person.
Original: The dormice were kept and raised either in large pits or ( in less spacious urban surroundings ) in terra cotta containers , the gliraria , something like contemporary hamster cages .
Simplified: The dormice were kept in large : wikt : pits or in terra cotta containers ( which were called gliraria ) , which were like modern hamster cages .