The Umbilicus Urbis was also known as the Belly Button of Rome. Some believe it was the external part of the subterranean Mundus which was the entrance to the Underworld.
The Milliarium Aureum was the marker in the center of Rome from which all distances where measured. The statement "all roads lead to Rome" referred to the roads leading to this marker.
The Curia Julia was the senate house of Rome. Construction started in 44 BC, but was interrupted by Caesar's assassination at the Curia of Pompey - where the Senate met during construction. The Curia Julia was completed in 29 BC.
The Temple of Vespasian and Titus was started during the reign of Titus and completed and dedicated by his brother Domitian in approximately 87 AD. It was built to honor the Flavian dynasty of Vespasian, Titus, and Domitian.
This small shrine, dedicated to the Etruscan goddess Cloacina, honored the divinity of the Great Drain or Sewer of Rome (Cloaca Maxima). Coins from 42 BC. give a pretty clear image of what the shrine originally looked like.