My guy friend and I will be celebrating his birthday at a concert in Chicago in September. I would like to surprise him with an "add-on" to the weekend by choosing a romantic lodge of some sort within several hours of the chicago area. Lake, fire, hot tub...the like. Any suggestions?

Check out the American Club in Kohler Wisconsin.
Along with the Four Seasons Chicago it is the only AAA 5 Diamond award lodging in the midwest.
It is the home of the Kohler bathroom fixture company and the rooms are bathroom-centered in many ways, every kind you can think of. I would guess they must have saunas and/or nicer jacuzzis in some of the rooms.
We've never stayed in the fancier rooms. Beautiful grounds, beautiful area close to Lake Michigan.
That's the best you'll find close to Chicago (145 miles).

There's the Abbey in Lake Geneva.

The Abbey is tired. Not upscale anymore.
Try Geneva Inn or French Country Inn. PJ

Check out some places in Galena,IL; Eagle Ridge might be what you're looking for.

Another vote for Eagle Ridge in Galena. Used to have a "country house" there when we lived in Chicago---just about 3 hours and very much in the country---lake, fireplaces, hot tub, indoor/outdoor swimming pool, good restaurant, nice little bar.

You guys rock....this eagle ridge place might just be the ticket! I LOVE FODORITES!