Eldorado Springs Resort

it's a historic 1905 spring-fed pool + resort at the mouth of eldorado canyon, ~15 min south of boulder, with a historic ballroom that hosts weddings and private events. the ballroom seats up to 200 guests. no required vendors, they'll give you a recommended list, and the pool next door may be available for private use depending on season. the setting is the sell, dramatic canyon walls and pines, people call the views incredible. big caveats though: a review says it's day-use only now (no overnight lodging on site, so guests stay in boulder), the vibe is casual/family/public (pool crowds, noise, dogs), and the approach is a narrow dirt canyon road, plan guest transport. treat this as a 'call them' option if the canyon look is what you want. the ballroom can hold up to 350 guests for a standing reception.