As long as I was there, I decided to walk down that street on my own. A tram ran down the middle of the street, but I think otherwise it was supposed to be a pedestrian street.
There were several Christian churches here and many buildings from the 19th century and possibly earlier.
This church was just off Istiklal street on a side street.
It wasn't open, but this foyer was quite pretty.
Here's another shot of the ceiling.
Here you see one of the trams coming down the street.
A quieter side-street. You can see the tram in Istiklal Street in the background.
Another Christian Church.
Looking back towards the main street, the arcade forms a courtyard in front of this church.
Another church, which was accessed by these steps leading down to it.
This wall and gate separated this church and the steps from the street.
When I got back to the hotel, I did call the tour company and made a reservation to do a full-day tour with them the next day.