Why is ancient Rome a significant ancient civilization?

This can be seen in the legacies of the Romans in religion, the alphabet, language, the calendar, law, architecture and literature.

Christianity developed from a religion among a small group of Jews (who lived in Judea, which was part of the Roman Empire) into a mass religion in the Roman days. It spread around the Roman Empire. It became state religion. Catholic Christianity and Orthodox Christianity developed during the Later Roman Empire. They were originally called Latin or Western Christianity and Greek or Eastern Christianity respectively. The former was the main form of Christianity in the western part of the Roman Empire and the latter was the main form of Christianity in the eastern part of the Roman Empire.

Western European languages have adopted and adapted the Latin alphabet. The only letters in the English language which do not come from the Latin alphabet are J, U and W.

Italian, French, Spanish, Portuguese, and Romanian are languages derived from Latin (Romance languages). Many Latin words or words of Latin origin have entered English via two routes. One was that Latin was the language of the church in the Middle Ages. The other was the Norman conquest of England. French became the court language and many French words entered into the English language. These words are usually of Latin origin.

Many international words in medicine, law and theology are Latin.

The calendar we use is the Gregorian calendar. It is named after the minor modifications made by the calendar instituted by Julius Caesar (Julian calendar) by Pope Gregory XII in 1582. Therefore, we basically use the Roman calendar. We also use translations of the Roman names for the months.

Roman law became influential through the Corpus Juris Civilis, a collection of books which reviewed imperial laws going back 400 years (to the time of Hadrian) and was commissioned by the emperor Justinian I. It scrapped obsolete or unnecessary laws, made changes when necessary and clarified obscure passages. Its aim was to put the laws into books (previously they were written on many different scrolls), harmonise conflicting views among jurists which arose from centuries of poorly organised development of Roman law and have a uniform and coherent body of law. It was rediscovered in a library in Pisa in 1070. It became the foundation of the training of the nascent profession of lawyers in Europe in the Middle Ages and Renaissance. It has been used to compile the civil law of many modern nations.

The Romans influenced European architecture, sculpture and painting until the early 20th century. They influenced the art of the Renaissance (14th-15th century) Baroque (17th-18th century) and Neoclassicism (18th-20th century, and is still sometimes used today). Palladian architecture was also based on Roman architecture. It was popular from the 17th century to the 20th century and was often used for public buildings. Latin literature was very influential in European literature until the mid-20th century.