In 1598, Shah Abbas I moved the Safavid capital to Isfahan and launched a building program that transformed it into one of the largest and most beautiful cities in the world. The Naqsh-e Jahan Square, the Shah Mosque, and the Ali Qapu Palace were constructed as the centerpiece of a planned urban design accommodating an estimated 500,000 residents. Abbas reformed the military with gunpowder units, established diplomatic relations with European powers against the Ottoman Empire, and promoted trade through Armenian Christian merchant networks. The Persian proverb 'Isfahan is half the world' reflected the city's reputation during this period.