This mosque is located in the Old Town (Kastel) near the main (western) gate and the town walls. It was built of cut stone and covered with a pyramid roof imitating a dome under the eternit. A stone octagonal minaret was raised along the right wall; its height is 16 metres and was one of the most beautiful in Herzegovina. It was built in 1726 as a waqf (endowment) of Osman Pasha Resulbegović. The builders were masons from Dubrovnik. It contains elements of the Mediterranean architecture. It is the biggest mosque in Herzegovina. Before he war, the mosque was a heritage site. Osman-Pasha also raised a maktab and madrasa as the mosque outbuildings, which were the first educational institutions in Trebinje. The mosque was destroyed during the last war. The cornerstone for the new mosque was set on May 5, 2001. The ceremonial opening of the mosque took place on July 15, 2005. Today Osman-Pasha’s Mosque is identical to the one that was demolished by dimensions and materials used in its construction.