Omis, the town of contrasts, both natural and historical. It was founded and grew on the steep slopes of the Omis Dinara mountain, surrounded by the river Cetina in the north-west, and the sea in the south and south-east. It has grown on the outskirts of the Omis castle, built high above on the mountain. Due to permanent threats from the inland, as well as from the sea, the existing castle "Fortica", with a military crew in it, and supporting tower “Visec” in the canyon of the river Cetina, were not enough for the town's defense. So in the Middle Ages, Omis was encircled by walls, fortified with strongholds on the eastern, land side, and the fortress "Mirabella" on the north-western side. Only when it was surrounded and fortified by walls it became a “town”, but not in the true sense at that time, because a "town" in those days needed a Bishop's residence, and that never happened. This medieval town was named Olmissium, Almyssium, and later, under Venetian’s rule Almissa.
Piracy was the reason for the significant economic prosperity of Omis. From the middle of the 13th till the beginning of the 15th century, the citizens of Omis, as excellent seamen, monitored all navigation on the Adriatic Sea, endangering, generally, Venetian ships and their properties in Dalmatia, as well as ships of the Kingdom of Naples. The pirates of Omis were charging fees for free navigation. Omis pirates were extremely dangerous, especially under rule of powerful Omis rulers - the dukes of Kacic. In that time, Omis was known as a dangerous nest of pirates, as were Saracens on the Mediterranean Sea or the Tatars on the Black Sea. As they attacked the Crusaders too, Pope Honorius III undertook a crusade against the pirates of Omis in the year 1221, which Omis won! The second war, in year 1228, they lost, and came to be the end of dukes Kacic.
In the 15th century they accepted the rule of the Venetian’s, but at the same time, kept their autonomy. They paid taxes to Venice, and often had skirkishes with the Turks in the inland to whom they had to pay occasional taxes. There is a famous legend about Poljica’s heroine Mila Gojsalic, who, with help of Poljica people, managed to defeat the Turks. She was perpetuated by many Croatian artists, among them is famous Ivan Meštrovic, whose sculpture decorates the position in Poljica with an unforgettable view over town of Omis.
Every year at the beginning of July, Omis hosts a grand festival that lasts for a week i honor of their pirate ancestors under the name of "The Pirate Nights of Omis". Apart from free concerts, free samples of the authentic food that can be ordered in the restaurants of Omiš, a costume party for children, and those who like to feel like them, Omiš organizes a sea battle in the port of Omis to depict the way their ancestors once boarded and took over Venetian ships, including explosions, sword fighting, and people jumping off the ships!
Also at the beginning of July, the festival of Dalmatian "Klape" (a cappela groups) starts. A large number of vocal groups from around the country, come to Omis to compete for the most prestigious award in the "Klapa" world. Authentic Dalmatian songs fill the dim lit streets of Omis during the nights, forming a most romantic setting, enjoyable to all that appreciate fine music.