Check out the "Private Guides" section of the Board. Lots of recommendations there from those of us who have used private guides. Definitely info there for Istanbul and Barcelona. Not sure what other ports you hit?
In Istanbul, if you didn't see the Cisterns and the Spice Market, both get rave reviews. Also, Suzanne has previously posted a number of restaurant suggestions for Istanbul lunch or dinners.
🚢 Cruise with your favorite Keene Luxury Travel Staff Member! 💰 5% KLT Reward plus Shipboard Credit available (amount varies per voyage)! 💲 Offering Enhanced KLT Rewards on voyages hosted by Ngaire & Clay!