I spent 3 full days in Istanbul, staying at Best Western Hotel Spectra which is in an excellent position. The breakfast room looks over the Blue Mosque and the Bosphorus.

I visited the usual sites
The Blue Mosque

Sancta Sophia

Down to the Bosphorus and the Bucolean Palace wall (AD830)

and visited the Great Palace Mosaics Museum (AD500)

Acoss the Bosphorus by ferry (several times) to Uskudar and Kadikoy on the Asian shore.
Here is a view of Istanbul from Kadikoy

and the Fish markets at Uskudar

A morning was spent at the Topkapi Palace
The Main gate

The beautifully tiled Antechamber in the Harem

Below is the Fourth Court

from where there is a great view over the Bosphorus

and of course I visited the Bazaar
Then on Tuesday 22nd April I went by bus to Eceabat, my base for visiting Gallipoli