Ecuador owns colourful history that is adorned with the charms of ancient Inca sites and colonial cities. The story begins with arrival of the Incas conquering the various tribes in the mid-15th century. However, the advanced cities such as Ingapirca could not stand the attack by the Spanish in the 1530s, the ruins of which still stand today. The Spanish state, Gran Colombia ruled the territory that incorporated Colombia, Venezuela, Peru, Panama, Brazil and Guyana. With several rises and falls of power, a peace treaty was signed, and boundaries of Ecuador were permanently established in 1831 with the fall of Gran Colombia. However, relations between Ecuador and Peru have been stressed ever since. After economic glory with the discovery of oil and many years of military rule, the country got its first presidential elections in 1979. With power straddling between left and right for over two decades and deteriorating economic situation of Ecuador, USD was adopted as the official currency dropping its own currency Sucre.