>>35789755Three reasons:
1.) The map of Beta Johto is basically all of japan, and the Ruins of Alph were placed where modern Hiroshima is on that map
2.) The actual main structure for the Ruins looks like a real-life memorial found at the bombing site (seen here:
>>35789889). If you can't see it, the roundish dome on the top of the Ruins of Alph structure looks like a scaled down version of the domelike lattice on the real monument, and the rest of the 'tower' is actually the broken walls of the monument merged into a single building around the dome.
3.) The interior of the Ruins features different carvings from what are in the retail version of the game: what was present in the Beta were pictures of humans, images of what looked like fire or explosions, wind apparently knocking over objects (buildings?), and a bunch of other cataclysmic stuff that could be interpreted as a depiction of a bomb going off in the area.