When I visited the Seattle Sculpture Park in Downtown Seattle, I noticed the wonderful public building/museum space on the grounds and immediately thought, "That's where I want to get married!"
Sure, I lack both an engagement ring or a finance, but after 27 years, I've finally got an inkling of what kind of wedding I want (most girls figure this out by age 12).
The building is big enough to fit 50-ish people, and has an open floor plan with glass walls that look out on to the Seattle skyline and waterfront. With a peaked roof and vaulted ceilings, the place has an airy, modern, almost cathedral-like feel. Plus, it looks like one could set up a lovely wedding there and quickly convert it to a reception hall as well.
The building can be reserved through the Seattle Parks Department. You'd have to check with them on rental fees, however, SPD rental fees are usually very reasonable.
Bonus points for the space: Plenty of near-by street parking, hotels, restaurants, and activities for your guests. Load-unload area is available. You'd have spectacular (and unique) wedding photos. If your guest's kids get noisy, they can always go play in the park while still in view of their parents at the reception.