Magelang is a city, and regency, immediately north of Yogyakarta. The massive temple complex of Borobodur is located a short distance from the city, although most people base themselves in Yogya for a visit to the temple.
The city was founded some time around the ninth century, but most of the sights of the town itself date from the Dutch colonial period. The city itself doesn't figure much on the tourist trail, since visitors going to Borobodur from Yogyakarta never even pass through town. It can, however, be a good base if you also want to explore the Dieng Plateau, which can be a very long day-trip from Yogya.