Ephesus was the supreme metropolis of Asia in the ancient world, and the center of the travel and the trade. Because of its authentic Christian tradition and connection to Paul, Ephesus has become one of the most popular sites that people travel to. Even though Luke would have introduced and spread Paul's activities in Alexandria and Rome, which were popular cities that became a hub of Christian activity, he did not. Luke thought that Rome was not a center of missionary activity for Paul. After his successful preaching in Ephesus, Luke considered Ephesus a great center of Christian activity because there was an epistle to the Ephesians from Paul. Also, in the Pauline Corpus, there are many further references are found about Ephesus.  
I fought with beasts at Ephesus.1Cor 15:32
I will stay in Ephesus until Pentecost.1Cor 16:8
As I urged you when I went into Macedonia, stay there in Ephesus so that you may command certain men not to teach false doctrines any longer.1Tim 1:3
May the Lord grant that he will find mercy from the Lord on that day! You know very well in how many ways he helped me in Ephesus.2Tim 1:18
I sent Tychicus to Ephesus. 2Tim 4:12
Moreover, Ephesus shares a connection with Johannine Christianity and it is included in the list of the seven churches of Asia Minor: Ephesus, Smyrna, Pergamum, Thyatira, Sardis, Philadelphia and Laodicea. Also, there are some scholars who have claimed that Mary spent her rest of life in Ephesus. 
Ephesus was initially built on a river bend, but later on, it became a full harbor near the Cayster River, on the western coast of Asia Minor, where Turkey locates nowadays.  In Roman times, it was situated on the northern slopes of the hills, Coressus and Pion, and south of the Cayster River. From the silt, a fertile plain has formed and it is now six miles from the Aegean Sea. Throughout the years, the city has shifted in five distinct locations. The Apostles Paul and John were familiar with the city, "Ephesus III", which was the largest area of the five. The five areas where Ephesus was located are: 
|Ephesus I||Aya Suluk (St. John Area)|
|Ephesus II||Artemission area|
|Ephesus III||Port of St. Paul|
|Ephesus IV||north of Aya Suluk|
|Ephesus V||Selçuk area|
Ephesus was a great seaport. The city was located at the convergence of three land routes with a shipping lane. The land routes that converged on Ephesus were:
- The Colossae / Laodicea road (went east towards Babylon)
- The road to Sardis and Galatia (northeast)
- The Smyrna road (north) 
Some scholars assume that there were about 250,000 inhabitants during Ephesus III, which was perhaps the fourth largest of its day behind:
Ephesus was the largest city, as well as an economic stronghold in Asia Minor. It was also called the supreme metropolis of Asia even though some scholars have found an evidence that Ephesus' overall economic standing has been slowly declining. 
Archaic Period (900-560 BC)
Known as Miletus, Ephesus was not a well-developed village during Archaic Period. Many scholars assume that during the time of Heraclitus the philosopher, Ephesus had played a essential role as part of the Ionian Renaissance. Until the harbor was built in the city, it was a farming and trade village. Also, since this period, a significant cultic site to Cybele had developed.
- Cybele: It was an Astarte-like warrior-goddess with the sacred axe. However, later on, Cybele was assimilated with the Anatolian Earth Mother Goddess. Until in 205 BC, when the cult was brought to Rome, there was not much information about the cultic worship. There were some aspects of the cultic worship: the accession of Galli, which was self-emasculated priests and the use of immersion in a bull's blood, which was the practice that was taken over by Mithraism, a mystery religion which became popular among the military in the Roman Empire, from the 1st to 4th centuries AD. 
Greco-Lydian Period (560-290 BC)
According to Herodotus, a Greek historian who is regarded as the "Father of History" in Western culture, King Croessus (560 BC) conquered the city during 6th century BC, when he tamed the Ionian cities. Mining operations for gold and the minting of Lydian coins were established and these developments made the city trade with other cities. During this period the city built a Temple to the Greek goddess Artemis and redesigned the Cybele cultic site.
In 546 BC, the city was part of the Satrapy of Ionia. When Darius the Great, the third Achaemenid Zoroastrian emperor, died, Xerxes, the son of Persian King, was eager to conquer Greek territory with his great ambition. After battles in Greece, he honored the Temple of Artemis in 478 BC when he returned back. This was very unusual since the Persians destroyed many other contemporary shrines. In 466 BC, when the Persians were completely defeated, Ephesus became a tributary of Athens. The city restored the Artemission in 450 BC.
In 356 BC, Herostratos set fire to the Temple of Artemis at Ephesus in his quest for fame. After the big fire, Ephesus took a long time to recover. Even though Alexander the Great attempted to finish the half-reconstructed Temple, the city declined. It did not complete the restoration until Lysimachus took over after Alexander's death. Lysimachus established new colonists and renamed city after his wife's name, Arsinoë. However, the name didn't last. Building six miles of wall near the city, Lysimachus increased the prominence of the city.  
Temple of Artemis
Even though the temple of Artemis is separated from the city by about a mile and is 2400 meters east of the ancient harbor, it is the most important structure in the city. It is considered one of the seven wonders of the ancient world, and the temple of Artemis was dedicated to the goddess of the hunt. The temple is 425 ft. long, 220 ft. wide and 60 ft. high. Actually, there are two major temples for Artemis. One of them is the Archaic Artemission,Croesus's Artemission, which was built in 560-550 BC, and another is the Later Artemission, also known as the Hellenistic Artemission, which was constructed from 334 to 250 BC. Paul's successful ministry in this city was considered a threat to this very temple.  
"There is danger not only that our trade will lose its good name, but also that the temple of the great goddess Artemis will be discredited, and the goddess herself, who is worshiped throughout the province of Asia and the world, will be robbed of her divine majesty." (Acts 19:27)
Library of Celsus
Originally built in 115-25 A.D., the library of Celsus in Ephesus is one of the most famous structures in the city. The library was dedicated to Hadrian, who was emperor of Rome. However, there are some scholars who insist that the library was dedicated to Celsus, the proconsul of Asia. Because of its alternating open and covered spaces, round and triangular pediments, projections and recessions, many people love its exterior facade. The style is believed to be the standard architectural form for Roman libraries. The interior measures 70 by 80 feet and held approximately 15,000 scrolls. 
Ephesus is known as the home to a series of residential complexes, built from the first to third centuries, called the terrace houses, or Hanghauser. The houses were built against the mountain south of Ephesus and they were built on a slope with narrow alleys. Like apartment blocks, the houses shared walls with one another. Influenced by both Greek and Roman styles of houses, they were decorated with many frescoes and mosaics. Like houses nowadays, the terrace houses were divided by rooms; they had bedrooms, bathrooms, triclinium, and kitchens. The terrace houses were inhabited until the seventh century. 
Like other Greek cities, Ephesus had an agora. Because of its dimensions 360 ft square, the place is known as the "Square Agora." After a catastrophic earthquake in 23 CE, the Tetragonos Agora was built. However, later on, the agora was rebuilt in the third century CE in the Hellenistic style with continuous colonnaded porticoes and shops. The market is located next to the harbor and it was the main marketplace in ancient times. Some scholars assume that Paul worked at this place with Priscilla and Aquila in their tent-making business. 
In Ephesus, the theater played essential role. Holding about 25,000 people, the theater was built during the Hellenistic time and was restored by some other Roman emperors. Even though it was designed for theatrical performances, gladiatorial contests were allowed to hold in this place.
In Bible, when Paul was charged for destroying the Artemis and the temple, Demetrius gathered together and made a complaint against Paul as a group. Gathering together in the theater, the mob shouted "Great is Artemis of the Ephesians!" After that, the city clerk had to calm the people and made them dismiss. 
Riot in Ephesus
About that time there arose a great disturbance about the Way. A silversmith named Demetrius, who made silver shrines of Artemis, brought in no little business for the craftsmen. He called them together, along with the workmen in related trades, and said: "Men, you know we receive a good income from this business. And you see and hear how this fellow Paul has convinced and led astray large numbers of people here in Ephesus and in practically the whole province of Asia. He says that man-made gods are no gods at all. There is danger not only that our trade will lose its good name, but also that the temple of the great goddess Artemis will be discredited, and the goddess herself, who is worshiped throughout the province of Asia and the world, will be robbed of her divine majesty." When they heard this, they were furious and began shouting: "Great is Artemis of the Ephesians!" Soon the whole city was in an uproar. The people seized Gaius and Aristarchus, Paul's traveling companions from Macedonia, and rushed as one man into the theater. Paul wanted to appear before the crowd, but the disciples would not let him. Even some of the officials of the province, friends of Paul, sent him a message begging him not to venture into the theater. The assembly was in confusion: Some were shouting one thing, some another. Most of the people did not even know why they were there. The Jews pushed Alexander to the front, and some of the crowd shouted instructions to him. He motioned for silence in order to make a defense before the people. But when they realized he was a Jew, they all shouted in unison for about two hours: "Great is Artemis of the Ephesians!" Acts 19:23-34
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- Ephesus Tours Unknown Author. EphesusToursTurkey.com.
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- The Seven Churches of Revelation John Class. Revelation-Topical Study.]