Denver is a growing city full of new neighborhoods, restaurants, art galleries, breweries and shops to explore. But the excitement doesn't end at the city limits. Denver is surrounded by historic towns, striking mountains and interesting drives that make for unique day trips away from the Mile High City. "There are so many cool little mountain towns and mining towns so I'm always sending people on day trips," says Jordan Chavez, concierge at the Hotel Teatro in downtown Denver. Zeyna Aouad, social media coordinator at the Grand Hyatt Denver, agrees. "You don't have to go very far to see cool things."Although most of these places can only be reached by car, some are accessible via the city's extensive RTD light rail or bus lines. Many visitors also use Car2Go, a car-sharing service with a variety of parking stations around town. [Read: The 6 Best Denver Brewery Tours.]GoldenLocated 15 miles from downtown Denver, Golden, Colorado, is best known as the hometown of Coors Brewing, the largest single-site brewery in the world. Golden's charming downtown district and multitude of hiking and biking trails make this historic foothills town a popular destination with visitors and local Denverites alike. "That's an excellent day trip," says Sheila Gargan, concierge at The Westin Denver Downtown and a Denver native. "I send people up there to walk along the Clear Creek bike path and visit the Coors Brewery, which gives free tours and coupons to use later in town." Gargan also notes that Golden is easily accessible without a car as several methods of public transportation are available, including the light rail and bus systems. Once in Golden, visitors can rent bikes to explore the town and surrounding trails.Those who do have a car can visit Golden as part of the Lariat Loop, a 40-mile scenic and historic byway that also passes through the towns of Morrison and Evergreen, and features attractions like Buffalo Bill's grave, the Colorado Railroad Museum and the world-famous Red Rocks Park & Amphitheater. Idaho Springs and Mount EvansThe discovery of gold in this historic mining town 32 miles west of Denver prompted Colorado's gold rush in the mid-1800s. Visitors can poke around the antique shops and breweries that line Miner Street, conquer icy rapids on Clear Creek, try their hand at gold panning or wind their way up the Mount Evans Scenic Byway, the highest paved road in North America. The road passes Echo Lake, a popular area for hiking, picnicking and fishing, before coming to an end near the top of Mount Evans, one of the state's more than 50 famous "fourteeners" – peaks that reach at least 14,000 feet. "It's a beautiful drive, and I think it's special," says Paul Gonzer, the Art hotel's concierge. "And, if you want to go home and tell your friends you did a fourteener, then you don't have to clue them into the fact that you drove up most of it and only actually climbed the last 200 or so feet."It's important to note that the road past Echo Lake is typically only open from Memorial Day through Labor Day, and that even in the summer months the weather is often cold, windy and subject to drastic changes. LittletonJust 10 miles south of Denver, Littleton is home to antique shops, restaurants and parks. [Read: How to Plan the Perfect Weekend in Denver.]"I send a lot of people on the light rail down to Littleton, where you can go to the Carson Nature Center or the brand-new Breckenridge Brewery," Gargan says. "That's a great daytrip, especially for families."More adventurous visitors can also get to Littleton via the South Platte River bike path, a fun ride that takes just over an hour from downtown Denver. Rocky Mountain National ParkAlthough it's a 70-mile or more drive, Rocky Mountain National Park and its gateway towns of Estes Park and Grand Lake are the top choice for an unforgettable day trip from Denver, says Lindsey Koehler, deputy editor at 5280 Magazine, Denver's award-winning city magazine."There's simply no more beautiful or iconic scenery within a two-hour drive of Denver," Koehler explains. "It's hard to match the terrain and beauty of that."Outside the east entrance, Estes Park is home to the iconic Stanley Hotel and a cute downtown with fun events and festivals held year-round. Those who choose to drive the length of Trail Ridge Road during the summer months will find themselves in the tiny town of Grand Lake, where they can rent a canoe, fish, sunbathe on the beach or spend time in a local shop. BoulderMichael Schmidt, tour concierge at The Crawford Hotel, describes Boulder in one word: fantastic. Part historic homestead, part funky college town and part sophisticated city, Boulder is a favorite day trip for visitors of all ages and interests. From strolling and shopping on the pedestrian-only Pearl Street or tubing down Boulder Creek, to catching a football game at Folsom Field or dining at a handful of nationally recognized restaurants, one day in Boulder simply isn't enough. Luckily, at just 30 miles northwest of Denver, and with a variety of public transportation methods, multiple visits to Boulder are as possible as they are necessary. "I love sending people out to Boulder to check out that college town environment and do some hiking," Chavez says. [Read: The Best Things to Do in Denver.]Several easy hikes are located just minutes from downtown Boulder, including at Mount Sanitas and the ever-popular Chautauqua Park trails.Gargan also recommends planning a visit around the Boulder County Farmers Markets on Wednesdays and Saturdays in the spring, summer and fall, and sampling the taps at Mountain Sun and Twisted Pine breweries. Aouad suggests stopping by the Celestial Seasonings headquarters for a free tour demonstrating how their tea is made. To experience more of what Denver has to offer, check out the U.S. News Travel guide.