That arcitrave/moulding on the left is probably 1", and the cornice to the right about 3"
Spider at full sideways span probably 3'...can be 5-6" full span 'though.
edit...had an arachnophobe mate, who had one of those mothers in the house (they carry the young on their back)...he hit it with a broom, and it "shattered" into hundreds of spiders. He was a quivering wreck when we got back to his place.