It was made on 2b2t, the seed is well known: -4172144997902289642. FitMC makes a video where he shows what the original spawn looked like: https://www.youtube.com/watch?v=ksS00MCQPog

2b2t has used multiple seeds over its lifetime and has long since used custom (and not released) modifications to the terrain generator. I.e. this doesn't work all too well beyond spawn.