The spread of Christianity, from antiquity until today, on an animated map

What is going on with Celtic Christianity? Was it really as distinct from Roman Catholicism (and for as long) as the graphic suggests?

Also, why no Cathars/Albigensians in the south of France during the 12th & 13th centuries?

What blew me away was the proliferation of the Church of the East. I never knew Christianity had that much of a foothold in Asia. I wonder if geographically it appears more significant due to that region’s sparse population?

It's even more interesting when you think about Christianity not as a clear category, but as a cloud of practices, beliefs and institutions in a broader family of religious patterns.

Mircea Eliade asks how Christianity reinterpreted sacred history, myth, salvation. What does Christianity do with motifs older than itself, such as paradise, rebirth, sacrifice? In A History of Religious Ideas [0], he treats the emergence and development of Christianity, including Judaism, early Christianity, Gnosticism, late antiquity, medieval religious forms and also how it interacted with other traditions. I think it complements quite nicely the geographical spread of Christianity by also clarifying what kind of transformations of religious symbols make it recognisable as Christianity across such different contexts.

There's also "Darwin's Cathedral" [1] that analyses religion as group-organizing system, with a focus on Calvinism. Didn't go through it, but seems relevant. It was recommended by Robert Sapolsky in his Introduction to Human Behavioral Biology lecture series [2].

[0] A History of Religious Ideas - Mircea Eliade

[1] Darwin's Cathedral - David Sloan Wilson

[2] https://www.youtube.com/watch?v=NNnIGh9g6fA

During the last few years, I’ve been exploring Svealand, the central part of Sweden that contains Stockholm and some other provinces. The region contains many historical places, but I walk the countryside, away from the main tourist attractions. What has impressed me the most is the amount of ancient piles of ruble with vigilant, almost hostile churches next to them. There are rock paintings from prehistoric times still around, and many, many mounds and graves from the bronze and iron age, the region is literally littered with them. But I’ve never found a single extant statue nor statuette nor depiction of the old Norse gods.