The world is your oyster from that location. The trendy River North area is just across the river to the north, a very short walk. What kind of food and price range are you considering? Do you want something with a touristy Chicago “feel” to it? That area is so dense with fine dining it’s almost impossible to know where to start.
From the touristy perspective I’ll offer these:
Harry Caray’s is very good. It’s a signature restaurant that surpasses any common theme restaurant pitfalls. The pasta, especially the Vesuvio, is great and they have a full menu of good, traditional American/Midwestern fare. Steaks, chops, pasta, seafood…basically hearty meat and potatoes type dishes.
Deep Dish Pizza. The big names are all chains but it’s what most people think of when they want Deep Dish. On the linked map you want to find Giordano’s, Gino’s East, Lou Malnati’s and Pizzeria Uno & Due. Everyone has their personal preference and I’m not sure there’s a clear definition of which is best. Personally I like Giordano’s the best, it’s the cheeziest and has the most flavorful sauce. Gino’s has their signature cornmeal butter crust which is good but the place tilts a little to far on the gimmicky side for my liking. Lou Malnati’s ingredients are top notch, it’s probably the closest to a purist’s approach but I find the tomato sauce a little bland and the overall product a little too bready. Pizzeria Due (commonly considered superior to it’s sister Uno for some reason) is my least favorite of the options and their style tends to be a little closer to what I consider a thick crust pizza than a true deep dish. Lots of bread and a modest amount of cheese, the flavors are very good but Chicago-style deep dish I love is basically a Hot Cheese Pie…Uno and Due are the furthest from this.
All that said, if you decide to do the pizza thing I strongly recommend against the sausage version your first time, or at least get a small and mix and match. They tend to really go overboard with the sausage to the point that you get as much meat as you do cheese. Some people love this but I find it a little overdone. Pepperoni is a better experience.
Last, but certainly not least, order a Chicago-style cracker crust pizza to go along with the deep dish. The deep-dish tourist spots don’t make the best versions of this but if you want to get the full Chicago pizza experience you need to try this as well. Many locals think it’s superior to deep dish and the best places to find it make pizza that rivals any in the world. The cracker crust pizza (cut square!) can be truly epic.
Keep Mike Ditka’s in mind. I think the food and atmosphere here is fabulous. I prefer it to Harry Caray’s and their meatloaf is something to be cherished. It’s pushes the limits of walking distance depending on the state of your crew, it’s about 1.25 miles north, but it’s certainly doable if you like the idea of a nice summer evening stroll up the extremely energetic Michigan Ave or Rush Streets.
Morton’s is basically right across the street if you are looking for a classic steakhouse. I actually haven’t dined there, and it’s grown into a chain in it’s own right, but I don’t think you could go wrong with it if you wanted man-food the shortest possible distance away.
Gibson’s is the more famous and more exciting Steakhouse in Chicago but it’s also up north on Rush near Ditka’s. It’s a walk I wouldn’t mind but again it depends on the needs of your group. I love it there and the scene is unrivaled. It’s a celebrity favorite for good reason. If you want to really do it up and make it special this place is worth the trip. Bring a fat wallet and a empty stomach and pound the huge portions and huge martini’s like a fat cat.
I’ll stop there, none of those places are obscure and I’m sure you could have tracked them down on your own but you didn’t give me much to do on. Narrow it down a touch, especially as far as your definition of “walkable” and “moderately priced”. The area is utterly saturated with first rate dining so this thread could go on all day.