By Plane: The closest airport that serves Boulder is the Denver International Airport. From Denver airport, you can get on a private bus or a taxi to reach Boulder. It takes approximately 70 minutes to reach Boulder from Denver International Airport. Alternatively, you can also drive from Denver. The route offers some of the best views.
HOW TO GET AROUND BOULDER
By Bus: The city is well-connected internally through the RTD bus system. They help in easier and faster transportation.
By Car: Only if you are planning to travel for a long distance inside the city, rent a car. Also take the huge traffic and the pedestrian population into consideration.
By Bicycle: It is a common practice for the locals of Boulder to commute within the city on a bicycle. And there is also a concept called Bike sharing program. They cost even cheaper.