Climbing is an integral part of cycling, unless you live somewhere dead flat then the gradient is what forces you out of a comfortable aerobic effort into a threshold or anaerobic zone. The ability to familiarise the body with this change in effort and learn how to manage the pace and exertion is paramount if you want to continue after the climb with out it taking too much energy out of you.
Cadence is important for improving efficiency and for the body to learn how to generate high levels of torques without to much strain. The ability to manage your cadence will also help you manage changes in gradient and terrain and keep good momentum throughout the race.
Long steady rides
Long steady rides are the bread and butter of cycling. They are the foundation of your fitness and not only help you develop the endurance to complete long races, they also build endurance base that will enable you to recovery quicker and support a high volume of training. These generally are kept at a steady effort/HR throughout but over time increase in volume or duration.
Working at just below the effort that you begin to accumulate lactate, over time increases the point at which lactate accumulates. this means you can hold a higher intensity for a longer period before you begin to fatigue.