Emperor Kahless Military City was a settlement on the planet Qo'noS and was a notable military academy on the Klingon homeworld. In the year before the House of Mogh moved to Khitomer, a young Worf, son of Mogh who was six spent time at the academy where he met Malach aged eight and the pair mde a blood oath together. This stemmed a long lasting friendship between the two as the oath was both witnessed and official. (DS9 novel: Vengeance) Presumably, it was named in honor of Emperor Kahless the Unforgettable.