In addition to the Certosa del Galluzzo (which I visited for the second time after many years) I have experience of some other Italian Carthusian monasteries, more or less famous: Pavia, Naples, Padula, Calci, Pontignano near Siena. In none of these have I been able to take advantage of a guided tour so complete and so easy to practice (but I haven't been from Pavia for decades, so things could have gotten much better there): summer and winter, every day of the week except Mondays, visits are possible at set times by accessing at the moment, without reservation (I don't know if, by reservation, guided tours are also possible in other languages).
This admirable service is due to the so-called "Community of San Leolino": a mixed community of lay people and religious, whose institutional seat is at the Pieve di San Leolino (Panzano, hamlet of the municipality of Greve in Chianti) and which was commissioned by Archbishop of Florence to administer the abbey after the departure of the last (Cistercian) monks in 2017.
This way, the peculiarity of the abbey can be fully known: the visit (included in the entrance ticket, at a fair price of 5 euros) lasts almost an hour and a half, and concerns all the practicable parts of the abbey (therefore, for example, not the dungeons).
The visitor is thus able to get to know the peculiarities of the attraction: the story of Niccolò Acciaioli, rich and influential Florentine merchant, founder of the Certosa, is illustrated. The precious frescoes by Pontormo are illustrated in depth, executed in 1523 in some arches of the larger cloister of the Certosa, and now brought to the building called "Palazzo Acciaioli". The frescoes are partly ruined by time, but in my opinion they have acquired a new charm through the white surfaces that have replaced the lost colors. The harsh discipline of the Carthusian monks is illustrated, as the distinction between full-fledged cloistered monks and the so-called "conversi" who can have links with the rest of the world: a distinction that is reflected among other things in that of the two juxtaposed churches, for cloistered and not. You can appreciate the fascinating succession of cloisters (three) from the smallest to the largest, which also here follows the rigorous architectural rule of the order founded by San Bruno of Cologne. You can visit one of the monks' cells, large and airy, also equipped with a personal garden, which somehow compensated them for their hard life of penance. You can admire the choir stalls in the cloistered church, with their precious inlays.
At the end, the visitor enjoys the satisfaction coming from having fully understood (as far as possible for a non-specialist) the functioning not only of this "machine" of penance and industriousness, but of all similar ones, scattered around the Europe.