Banja Luka is the largest city of the Republika Srpska entity and second largest city in Bosnia and Herzegovina after the capital Sarajevo. The city lies on the River Vrbas and is well known in the countries of the former Yugoslavia for being full of tree-lined avenues, boulevards, gardens, and parks. According to the 2013 census the City of Banja Luka, has 185,042 inhabitants.

Banja Luka has a moderate humid subtropical climate which borders a humid continental climate, with cold winters and warm summers. The warmest month of the year is July, with an average temperature of 21.3 °C. The coldest month of the year is January, when temperatures average near freezing at 0.8 °C.

Due to its long history, Banja Luka is rich in culture. There are several museums including the Museum of Bosanska Krajina, the Ethnographic Museum established in 1930, and the Museum of Modern Art of Republika Srpska which is also called MSURS the Museum of Contemporary Art. Banja Luka is also the home of the national theatre and library, both dating from the first half of the 20th century, and of numerous other theatres. The headquarters of the Archives of Republika Srpska is situated in the building known as Carska kuća or Imperial House, build around 1880. It has been in continuous public use longer than any other structure in Banja Luka.

The natural beauties of the surrounding area guarantee the city of Banja Luka a good position in tourism. he city and surrounding area boast a number of popular tourist attractions. Among the most famous are the pools, thermal springs, and spas in the region. Due to its parks and over 10 000 trees Banja Luka was once nicknamed the "Green City".

Trebinje is the southernmost municipality and city in Bosnia and Herzegovina. Located in East Herzegovina, it is part of the Republika Srpska entity, and its population numbers 31,433. The city lies in the Trebišnjica river valley, at the foot of Leotar, some 30 km by road from Dubrovnik on the Adriatic coast.

There are several mills along the river, as well as several bridges, including three in the city of Trebinje itself, as well as a historic Ottoman Arslanagic bridge nearby. The river is heavily exploited for hydro-electric energy.

After it passes through the Popovo Polje area southwest of the city, the river - which always floods in the winter - naturally runs underground to the Adriatic, near Dubrovnik. Trebinje is known as "the city of the sun and platan trees", and it is said to be one of the most beautiful cities in Bosnia and Herzegovina. The city is economic and cultural center of the region of Eastern Herzegovina.