Hi,

so back in the Ancient times Adriatic was on the tip of the amber road, stretching from the Gaul and Germania, which Greek cities wanted to get their hands on. Greeks established a couple of cities Lissa (Issa or today Vis) and Faros (today Hvar island) as emporiums (trading ports). Most of that colonization of Adriatic happened from 395 BC onwards. That colonization happened really late due to the fact that there were some strong Illyrian tribes on the Easter Coast of Adriatic, most notably Liburnian tribe that is notable for it's thalassocratic rule and their naval control of Adriatic. Other tribes were Delmatae, Iapods and other.

With Rome becoming a power, Adriatic coast, mostly Dalmatia, was really interesting due to it being close to Rome. According to some historians, it would take you a five day travel from Salona ( today Solin, next to Split) to get to Rome. That fact is really close for comfort for Roman people. Not only that but you have said tribes that can raid the coast pretty easily. Roman military started to pacify Illyria pretty early with some places, such as Istria being incorporated into Italy early on.

Most of the pacification was successfully done during the period of Julius Caesar and Octavian. You can read about Dalmatian cities such as Salona in Caesar's Comentarii de Bello Civili in Book 3 point 9. where he says:

But after the departure Of the Liburnian fleet, Marcus Octavius sailed from Illyricum with what ships he had to Salona, and having spirited up the Dalmatians, and other barbarous nations, he drew Issa off from its connection with Caesar; but not being able to prevail with the council of Salona, either by promises or menaces, he resolved to storm the town. But it was well fortified by its natural situation and a hill. The Roman citizens built wooden towers, the better to secure it; but when they were unable to resist, on account of the smallness of their numbers, being weakened by several wounds, they stooped to the last resource, and set at liberty all the slaves old enough to bear arms; and cutting the hair off the women's heads, made ropes for their engines. Octavius, being informed of their determination, surrounded the town with five encampments, and began to press them at once with a siege and storm. They were determined to endure every hardship, and their greatest distress was the want of corn. They, therefore, sent deputies to Caesar, and begged a supply from him; all other inconveniences they bore by their own resources, as well as they could: and after a long interval, when the length of the siege had made Octavius's troops more remiss than usual, having got an opportunity at noon, when the enemy were dispersed, they disposed their wives and children on the walls, to keep up the appearance of their usual attention; and forming themselves into one body, with the slaves whom they had lately enfranchised, they made an attack on Octavius's nearest camp, and having forced that, attacked the second with the same fury; and then the third and the fourth, and then the other, and beat them from them all: and having killed a great number, obliged the rest and Octavius himself to fly for refuge to their ships. This put an end to the blockade. Winter was now approaching, and Octavius, despairing of capturing the town, after sustaining such considerable losses, withdrew to Pompey, to Dyrrachium.

This is considered by modern historians to be the main reason why Caesar elevated Salona to the status of colony and reduced the status of Issa. There are similar cases with other cities like Pola that sided with Brutus and Caesars killers, and was razed by the Augustus and later rebuilt, or Segnia that was important in Augstus' invasion into territory inhabited by Iapods.

Furthermore Rebellion of Two Batons that happened in the interior of now province of Dalmatia stopped and basically cancelled Augustus' planned invasion of Bohemian lands. That was last time Romans had issues in the region and they created a strong military presence due to it's strategic position.

A lot of progress was made after Publius Cornelius Dolabella, (consul in year 10 AD) during his tenure as a governor of Dalmatia, built a network of roads between the cities connecting them to the capital of province, Salona.

That also saw founding of multiple veteran cities such as Pons Tiluri.

Further improvements and reconstruction of the cities happened when emperor Trajan passed through the province on his way to Dacia.

Last stop in Roman development of the province happened when Diocletian built his palace near Salona at the place that is today Split. It is certain that he rebuilt a lot of things in Salona as well. One of the last emperors of the Western Empire Iulius Nepos died in the Diocletian's palace.

I think this covers Ancient building, now let's get to destruction.

During 7th Century Slavic and Avar forces managed to destroy a lot of places. They destroyed biggest city on the coast, Salona, which made people flee to the Diocletian's palace and create what is today Split. You can read about this account, which is incredible story, in Thomas the Archdeacons Historia Salonitana minor. Other medieval cities that were created in such manner also number Dubrovnik that is continued from Epidaurum that was destroyed in a similar manner as Salona.

Some cities just continued exist and develop, such as Zadar, whose ancient remains were destroyed in the Allied bombing raid at the end of the World War II. In this group we can also put modern Vis (which became important after British restored a lot of places and built a couple of forts in Napoleonic Wars) and Senj (ancient Segnia) and Nin (ancient Aenona that had biggest Roman temple on the coast).

Other cities, such as Šibenik were founded later by Croatian kings.

Some architecture was preserved by continued to be used such as Cathedral of Saint Domnius in Split that was originally Diocletian's mausoleum. (Ironically Diocletian put Domnius to death) Other architecture was lost to time, until recently. Great example of that is Augusteum in Narona that holds 14 statues of imperial persons and as such is currently biggest collection of those statues in one place in the world after Rome. Augusteum was rediscovered in the 1990s after being lost for more than a thousand years.

I think this shows that this was lively area and as such is really small, but to key persons it was important from strategic reasons, that enabled a lot of construction work and by extension it is now a great archeological dig site. But that is what you have everywhere, in Greece, Italy, Spain, France and so on.

Sources:

Caius Iulius Caesar, Comentarii de Bello Civili (Translated to multiple languages)

Cambj, Nenad, Antika Zagreb, 2002. (In Croatian)

Cambj, Nenad Greeks and Illyrians in mutual civilizational contact, Zagreb 2010. (I think this can be found in English)

Suić, Mate. Antički grad na Istočnom Jadranu, Zagreb 1976. (In Croatian)