In Part 2, Chapter 3, it says that the trial takes place in the last sessions of the Assize Court. Assize means legal seat or legal session. Most assize courts are obsolete. But I think France and Algeria both still use them. Although it never explicitly says where the trial is taking place, it must be in Algiers since that is where Meursault lives and the judge makes a reference to this when announcing Meursault's punishment. Meursault hears him begin with "in the name of the French people," and then hears that he is to be decapitated. Algiers was a French colony from 1830 to 1962.