It’s the national capital in all but name, so getting to İstanbul is easy.
There are currently two international airports IST (Ataturk International Airport) & SAW (Sabiha Gokcen International Airport)
Nationals of the following countries (among others) needed to obtain an electronic visa before their visit: Australia, Canada, China, Ireland, Mexico, Netherlands, Norway, Portugal, Saudi Arabia, Spain, Taiwan, UK and USA. These visas were valid for between 30 and 90 days and for either a single entry or multiple entry, depending on the nationality.
Your passport must have at least six months’ validity remaining.