It is said that the knowledge of Church history is a consolation. Most often this is meant in the sense that, for those who are troubled about the Church in the present age, all you have to do is look back at the history of the Church and you are sure to find an era that is as bad or worse than the present. I would suggest, however, that the consolation of Church history also applies to the good times. Reflecting on good times provides us with something to strive for and provides hope for the future. If we ourselves must suffer through the unhappiness of widespread laxity and apostasy, we can work for better times for future generations. In addition to being a theological virtue, the hope that the efforts of our lives will contribute to something better for our descendants serves the practical function of being a powerful motivator. It helps us through the grind of our daily work.
The most obvious examples of such better times, times that can serve as motivators for us, are the periods of great evangelization and the periods of great reform. We can look at the rapid spread of Christianity through pagan Rome in its first centuries. We can look at the rapid spread of the monastic reforms of Cluny and Citeaux (Cistercians) in the Middle Ages. Or we can look at the extensive missionary work of the Society of Jesus in Early Modernity, to cite just a few.
Yet, historical accounts of these periods can be somewhat abstract, especially for those of us with weak imaginations, and it helps to make use of visual aids. In particular, I find maps helpful. For example, it is known that in the 50-year period between 1098 when Saint Robert of Molesme founded the Abbey of Cîteaux and the death of Saint Bernard of Clairvaux in 1153, some 350 monasteries were founded or came under the Cistercian reform. A map of these monasteries (taken from here), including also the monasteries that came under the Cluniac reform, can be see below: