Northern Mongolia is the easiest region to travel outside of the capital, with most of the cities reached by paved road and rail lines. The 2nd and 3rd largest cities in Mongolia, Erdenet and Darkhan respectively, have almost hourly bus service from Ulaanbaatar and between each other, as well as stops on the Trans-Mongolian line of the Trans-Siberian Railway. Sühbaatar also is a stop on the Trans-Mongolian. All cities in the region have at least daily bus service from the Dragon Center in Ulaanbaatar. Due to the ease of travel in the region, only the furthest city of Mörön has regular flights, with as many as 3 flights a day from UB from all 3 domestic airlines during the peak summer travel period.