Blue Nile is one of the better places to find a vegan meal in Columbus. There are a number of vegan dishes on the menu and, although the prices aren't cheap, the food is very filling and you get a lot of it.
Also, the kitchen sends out free samples of other dishes when they bring out your meal. My waiter once brought me a sample dish that looked like it could be meat. I asked him whether there was meat on my injera and he laughed at me and said "no, it's eggplant" and then explained that the kitchen makes a point of only sending vegetarian samples to guests ordering the vegetarian dishes. In addition, he informed me that the kitchen is happy to split up a party's orders onto two separate pieces of injera if there are vegetarians in the group who are concerned about cross-contamination.