The Venore Corym Cave is located east of Venore in the swamp, here. You have to go up the stairs in the building there and then down the ladders, to prevent roping. The quickest way there is through the east Venore city entrance.
As a paladin of level 55+, skill above 80 and Royal Spears you can make good profit and experience (even 100k/h with stamina bonus) when hunting here with relatively low risk of dying. Just remember not to run like a mindless bot through the caves - just focus on one area filled with as many Corym Vanguards as possible. Particularly good spot is here (with the large cave north-east, but you will probably not need go there, Coryms respawn is fast).