Caesier's in East Pripyat

I presumed it's the port in the north area; I headed to that spot and found no portal. I followed the fence and there's a place  without fence that allows you to enter the water and head north towards the end of the map. Assuming I could walk this out-of-map area I ran to the place according to Plesskyn's guide/sahafiec videos.

via the portal in the container yard in the south west corner of Jupiter, which drops you close to the photo.

The best way to view the photo is to drop it on the ground and look at it through your binoculars. Hopefully you will recognize (or be able to find) the four locations. If not, see the East Pripyat section here:
[You must be registered and logged in to see this link.]

Yes, the River Port is in the north east. The portal to cross the river is in the small circular booth in front of the River Port buildings. It is above you, so you have to enter the booth and then jump. It doesn't matter if you don't use it, it is just more convenient than wading across! You only need to go there if the cache is in the one location on that side.

Another portal will appear down on the dock when you have found the cache, and that is your route out of East Pripyat.