Bloodborne: Guide to Finding Cainhurst, Ancient Ruined Castle [PS4]
This is another of the game locations that you may need to visit.
Trophy Guide / "Cainhurst" Objective
Finding this place not only serves to unlock the trophy, but it will also serve you to find special objects that you will need on other occasions.
Cainhurst is a hidden area of the game. To get access to it first of all you have to go to the "Forbidden Woods" and find the area with the dog cages (there is only one place in the woods with these cages, so you can't go wrong).
There is a hidden path behind the cages that leads into an underground cave, and from there into an area with a poisonous pond with some giant monsters. Avoid the giants that could kill you very easily and head directly to an exit tunnel that leads to a long staircase. Keep following this road until you come back to the first building in Yharnam, where the game started. Look well in the clinic because here you have to find the Cainhurst Summoning letter (Cainhurst Summons).
With the letter teleport to "Hemwick Charnel lane" where you fought the witch of Hemwick, in the area of the cliff. Crossing this area an intermission scene will start, then a transport will appear that will take you right to the castle.
Also check out the video below showing how to get to ancient Cainhurst Castle and good luck!
Alternatively, watch this video which shows the same thing: