Einstein's Principle of relativity is formulated in 4D Room, Though not in the Euclidean 4D Room. Einstein's notion of spacetime incorporates a Minkowski construction determined by a non-Euclidean geometry with 3 spatial dimensions and one temporal dimension, instead of the four symmetric spatial dimensions of Schläfli's Euclidean 4D space. Sebaliknya, https://ctmitalia.net/