Travelling from Paris to Switzerland to Rome by train at end of July. Arriving early afternoon from Paris to Berne (?) and leaving Berne (?) to Rome early morning. Haven't made train reservations yet. Have 3 non travel days in between to spend in Switzerland. Summit excursion main objective. Mountain village exploration and possible day trips to larger city also possible. Should I look at Lucerne area or Interlaken area? What cities as possible bases? What day trips possible? Looking to choose base area to start researching details.