Rome was located in central Italy along the Tiber River. It expanded throughout the Italian peninsula and into parts of Europe, North Africa, and Western Asia. The climate was typically hot and dry in the summer and mild in the winter. Roman religion began with many gods adopted from the Greeks and Etruscans, and later Christianity became dominant. Roman achievements included advances in architecture, engineering, medicine, literature, and law. The government was a republic that later transitioned into an empire led by emperors.