One of the most iconic monuments in Rome is the Victor Emmanuel II. You can't miss it even if you're not looking specifically for this building. You just somehow find these places in Rome. It is very close to Piazza Venezia. It's quite an impressive monument built by Giuseppe Sacconi in honour of Victor Emmanuel.
It's a massive monument towering in Rome built with corinthian columns and grand statues (especially of Victor Emmanuel on a horse)! It's very grandiose and in your face structure amidst the ancient structures and ruins in Rome. You can walk around inside and outside the monument. And there is also a terrace upstairs with restaurants and cafe so you can enjoy the view. If you want to see more panoramic view of Rome, you can opt to pay to take the elevator all the way up the building (entrance is at the back of the building to take the elevator). I opted not to do this as I was quite satisfied with the view from the terrace.