We will be arriving a couple days pretour and would appreciate advice on getting from IST in to the city. Our hotel is in/ near Topaki. Our arrival is scheduled for late afternoon.
We arranged a driver through our hotel to meet us at the airport and bring us to the hotel. The cost in May, 2022 was €60 for up to 4 people.
Havaist Airport Buses go to about 50 drop-off locations throughout Istanbul and you would take the Havaist Express Airport Bus #12 to Beyazit Square in Sultanahmet for 35 Turkish Lira (about $2 each). Topkapi Palace is about a mile from Beyazit Square, but your hotel can tell you how far they are from Beyazit Square. All Havaist Airport buses depart from a garage below the IST Airport terminal. You take escalators down to the Havaist buses and buy your tickets from the employee at the Havaist ticket booth with a credit card. No need to get any cash at the airport and no confusion trying to figure out the correct taxi fare in a foreign currency when you have jet lag.
Have a great Trip!
Or take the Havaist bus to Hagia Sophia and walk downhill to Topaki.
Edit: My above advice was for the Topkapi Palace area. Further research shows the Topkapi neighborhood is in the Fatih District, maybe a couple miles north of the Palace, of which I'm not familiar. Note the difference in spelling.