Riyadh is the capital of Saudi Arabia and is one of the larger cities in the Middle East. Due to money from the oil boom of the 1970s and 1980s, this wealthy city has developed over the years into an oasis of glass skyscrapers, gigantic shopping complexes, and a wealth of Riyadh museums that document the Islamic culture of Saudi Arabia. There are many attractions to explore in Riyadh. Al Bathaa is the heart of Riyadh Saudi Arabia and is the oldest part of the city. Most tourists visit Al Bathaa to shop in bazaars, visit Riyadh museums, mail a letter at the post office, or visit the bank. Not too far is the recently renovated Riyadh Zoo, which was established in 1957. Another popular attraction is the Al Musmak Castle. The castle, which represents the unification of the Kingdom of Saudi Arabia, was originally built in 1865 and has been renovated for tourism. Al Musmak Castle has many notable landmarks, including a mosque and a grand palace gate.