The city experienced fast growth from the outset. The first fortifications were built around it two centuries before Christ. As was the case with other polis (city-states) in Greece, Salonika was an autonomous district of the Macedonian kingdom and had its own governing authority. However, the king had the privilege to intervene in city affairs.

Thessaloniki came under the rule of the Roman Empire after the fall of Macedonia. It became a focal point of trade, as it was located on a Roman road linking Byzantium and Dyrrhachium (now Istanbul and Durres, Albania respectively). Around that time, it became the capital of a Roman district in Macedonia. The Romans constructed a large port, Burrow Harbor, in view of the city's growing importance related to trade. It survived until the 18th Century. Its remains can be seen in the city to this day.

Authorities built the famous Acropolis in 55 BC as a defensive structure against invasions.

Among the first centers of the new Christian religion, it is believed that the Apostle Paul held a sermon in a Salonika synagogue. In that period, a large part of the population of Salonika was Jewish.

The city's patron saint, Demetrius, who died in a Roman prison, is commemorated by the Church of St. Demetrius built on the prison site. He lived in the 4th Century and was reputedly a soldier in the Roman Army at one point. He is celebrated on October 26th of every year.

Salonika was under the yoke of the Ottoman Empire between 1430 and 1912, as was the entire region. Surprisingly enough, the Christian Orthodox religion was tolerated quite well, and the monasteries of Mount Athos even flourished at the time. Today, they are major attractions along with the Roman ruins and Turkish architecture.

Other points of interest include the Rotunda, erected in 305. It became a church in honor of St. George a little over a century later. Another remarkable monument is the Holy Wisdom church, completed in the 7th Century. Its interior is fascinating, adorned with a medley of beautiful paintings and murals. There are modern churches as well, and one is located in the street where the famous Byzantine Museum stands. It is important to see the White Tower, erected in 1430 and displaying authentic relics from the Byzantine and Ottoman Era.

The Archaeological Museum of Thessaloniki was officially completed on October 27th, 1962. It features ancient objects, classical art works, items from Derveni tomb excavations, sculptures, and other national treasures.

Today, Thessaloniki is a central harbor and major trade site. Major industries here include machinery, textile, refined oil, cement, and medicaments. Strategically located, it is an important transport route junction in southeast Europe.

The city has many traditional festivals, among which is the Video Dance. It displays the most recent trends in many art forms such as the creative aspect of media, movies and dance.

Thessaloniki is committed to international cooperation and has a wide-ranging network of twin cities, including Hartford, Plovdiv, Tel Aviv, Leipzig and Nice, among others.