Simplify the following text for a Grade 7 native English-speaking person.
Original: The construction of the capital city by Cyrus the Great , begun in 546 BCE or later , was left unfinished after Cyrus died in battle in 530 or 529 BCE .
Simplified: The building of the capital city by Cyrus the Great , begun in 546 BCE , but was left unfinished , for Cyrus died in 530 BCE .