Piazza della Rotonda represents today Rome's financial centre. Here you can visit the Pantheon with its Ancient architecture.

Other Tourist attractions in the area;

Churches:
The Pantheon, Gesu, Sant'Ignazio di Loyola, Santa Maria Sopra Minerva
Temples:
The Temple of Hadrian
Edifices:
Palazzo Borgheze, Palazzo Doria Pamphilj
Columns and Arches:
The Column of Marcus Aurelius (Marc Aurelio)