I didn't like this city, but the surrounding areas are interesting. Before, it was a compulsory stopping place for those travelling in a 4x4 between Addis Ababa and Bahar Dar or Gondar. Now, however, the road has improved and many decide to spend a full day in the car. Aeroplanes are also a very attractive option to avoid wasting time on this journey, which isn't worth it.
All the same, for those who want to take the time to travel peacefully, you should know that accommodation here is expensive and not very satisfactory, and the electricity is cut early in the evening. However, if you stay at Debre Marqos, you'll have the opportunity to visit the monastery of Debre Libanos, founded by Takla Haymanot, a monk who worked a great deal for the restoration of the dynasty of Solomonic kings in the 13th century. Nothing is left of the original church, but the site is very important in the Ethiopian Orthodox Christian religion.
Also in the surrounding areas of Debre Marqos, you can head to the gorges of the Nile, close to the village of Dejen, which you visit via a mountain road (in very poor condition), up to the huge bridge which spans the Blue Nile.