I am ashamed to admit this, but I always destroy a historical building/object if it gives me only a small trade bonus. However, the Ruins of Babylon will do more for you, and generally I regret having destroyed so many historical buildings for cash. My current roman empire, with ~130 territories lacks about 80% of the original unique buildings/places. I will do better next time though.

Just don't destroy it. You'll appreciate leaving it alone later on in the game. I mean, its EB, not vanilla. In vanilla it would be logical to destroy a building that does not give you any significant bonuses (such as only giving you a small trade bonus - 5% happiness is enough to prevent me from destroying a building) but this is EB, where historical accuracy triumphs over gameplay. It is up to you of course, but I suggest you don't do it.

P.S. Did anyone notice how high the trade bonus from the Herculean Pillars is (aka Gibraltar)? It simply massive. Gader is a Large City by now, and its is paying gargantuan upkeep as I have more than twenty full armies composed of mainly the best troops I can get, but it is still making 9,000 mnai per turn, with my 10 management & influence (8 command) governor. He is actually a Dull, Pessimistic, Drunkard (damn those Augury buildings!!!) Mercenary Italic General who rose to the position of first a Consul and then a Censor.