I am an Indian (Indian Passport) presently in Kano, Nigeria on a business visa. I am going back to Mumbai on 22 Sept by Turkish Airlines with a 12 hour layover time in Istanbul. We plan to see the city during this time.
Can I get a visa on arrival?
Turkey no longer issues Visa-On-Arrival, so to answer your specific question, no, you can't get one.
The Visa-on-Arrival has been replaced by e-Visa, where you can apply for a visa in advance via their website, and it is normally issued immediately.
However as an Indian citizen you are only eligible for an e-Visa if you have a valid Schengen or OECD member countries visa in your passport. Presuming you do not, then you will need to apply for a standard visa via a Turkish consulate.