Heaven's Secret Condition
In the last nine years, Ace had been in seclusion, and he chose the same place where he destroyed the Heaven Imposing Sky Lock while his other body was still outside. He chose this place because it was well hidden, and the Qi density and law presence in this place were far richer than anywhere he had ever been.
Furthermore, after the lock was unlocked, this place was empty, and there was no danger to speak of, so it was a good place for his training.
Moreover, while he was in seclusion, his avatar was keeping an eye on the ten continents' movements, and he knew everything about the merging of the continents and the current war against the Sea Kings Federation.
Ace had never expected that the Heaven Imposing Sky Lock was the main reason behind the Grand Split thousands of years ago not to mention unlocking it would make them return to their original state.