Rome Puzzle Trail from Castel Sant'Angelo to the Colosseum

A walking route held together by puzzles rather than by a guide. Each solved clue unlocks the next location, and the app supplies the history and the legends once you arrive. The line runs from Castel Sant'Angelo across the Ponte Sant'Angelo, through Piazza Navona, the Pantheon and Piazza della Minerva, past Sant'Andrea della Valle, then Piazza Venezia, Trajan's Forum and the Campidoglio, finishing at the Colosseum. Ten named stops with more turning up along the way. Because nothing is scheduled, the walk bends around the day. Stop for gelato by the Pantheon, sit down for a coffee in a square you had not planned on, and resume when you feel like it, including tomorrow. It runs whenever you open it, day or night. The app also carries a list of restaurants and shops chosen by the operator, which is the part that tends to get used after the last puzzle is done. It works for couples, families and larger groups, and for anyone who would rather solve something than follow someone.