As soon as you open the door a voice will call out to you and advise you to turn back as there are no longer humans in Old Yharnam for hunters, as he say, are already being part of the hunt.
Take the bridgeway to the left where you will be attacked by some Golems who seem to be afraid of
fire. At the side of the building there is a path leading down where more Golems and Hooded Golems are. As you move around, the voice calling out to you will fire at you from the top of a clock tower. For now, evade the shots fired at you.
You may take the stairs on the side which will bring you to a room. Continue on down to where you will find a make-shift bridge that will lead you into another room where Giant Crows and Hooded Lanky Beasts will attack you. Going through the room will lead you out to a yard. Cross the small make-shift bridge that will lead you to the bottom of the Clocktower where a Pistol-wielding hunter will be waiting--and which drops Bone Marrow Ash once defeated. After eliminating the Hunter, continue on down and climb the ladder on the side which will bring you to the top of the Clocktower where you will battle the Hunter who has been shooting at you. The Hunter moves extremely fast so you will have to make use of your dodges and side steps all the time. However, while doing this, be careful of dodging since the space is limited. Defeating this deranged Hunter will give you Powder Keg Hunting Badge afterwards.
After battling the Clocktower hunter, get inside the building by going down the ladder. As you make your way inside the building through beams and wooden platforms, you may pick up Molotov Cocktails and other items along the way. If you continue down towards the quadrangle, you will have to battle a mob of Golems and Hooded Golems. Try your best to lure a few beasts to you and eliminate them little by little since eliminating them all at the same time is extremely difficult. At one end of the room, you may find an altar. Upon inspection, you may pick up Ritual Blood.
Behind the altar is a passageway leading outside. If you take a right you will find a ladder that will lead you back inside the Church. Through here there will also be a staircase which will bring you to the third and second level of the church.
Behind the altar, taking a right will lead you down to an alley where Werewolves are waiting. At the end of the path, you will find a large wooden door which can only be opened from the other side.
Across the Church you will find another building where you will pick up a Beast Blood Pellet after beating the Wolf Beast. Going around this building will bring you to its entrance. As you make your way through, you will find a spiral staircase. From the second level, you will find a ladder to the side of the building which will take you atop a tower right beside the building entrance to Old Yharnam.
*(Note: At this building, you may continue on down by dropping at the side where you will find a hunter's Torch.
At the yard fronting the Clocktower, after jumping downwards to find the side entrance, you will find a chest with a Bloodstone. Also in the same building you will find a rifle spear from a from a hunter's corpse sitting on a chair.
At the back of the building, there will be a pathway downwards which will lead you to an arcade named the Church of the Good Chalice where an tomb rests at one end of the room. In this area, you will also find the Blood-starved Beast--a fast-moving-long-limb creature which swipes at you with its long, sharp claws. Dodging and side-stepping away from the beast will help. After defeating the beast, you will be rewarded with the Pthmeru Chalice.
After defeating the Blood-Starved Beast, you may return to cathedral ward to do more exploration.