First thing on my list was the Colosseum. Granted that it is a crowded tourist spot, but no trip to Rome is complete without a visit to one of the New Wonders of the World. I bought the "Skip the line" ticket (available online from the Colosseum's official website), which also gave me entry to the Palatine hill and the Roman Forum. In any case, be prepared for serpentine queues and for touts selling all sorts of merchandise.
NOTE: The Roma Archeologia Card and the Roma Pass also give you access to the Colosseum, Roman Forum and Palatine Hill. Please research whether you can "Skip the line" with these tickets.
It took me 3 hours to clear the queue and visit the Colosseum.
Word of advice: Take the "Colosseum by night" tour, which is a guided tour of the Colosseum's underground chambers. Make sure that you book it at least a month in advance as tickets are on first-come, first-served basis.
I passed by the Imperial Forum and Piazza del Campidoglio on my way to Fontana di Trevi (Trevi Fountain).
After visiting the Fontana di Trevi and the Pantheon, I walked to Campo de' Fiori, where the statue of Giordano Bruno watches over the bustling market beneath.
The first stop on the "other side" is Castel Sant'Agnelo, the walls of which can be seen even from across Tiber. This was a former papal fortress and castle, so I spent about 2 hours exploring the place. Don't miss the former Treasury Room, still intact with its huge chests and cabinets!
There is a narrow staircase that leads out to the roof of the castle, where I saw the statue of Saint Michael standing watch over the inhabitants of Rome. Did you know that this castle was once the tallest building in Rome?
My tour of Vatican was scheduled for Day 2, so I took the metro from Ottaviano metro station to Repubblica - Teatro Opera metro station. From there, I walked to the Baths of Diocletian, which was accessible by the Archeologia Card. This was one place where there were no crowds and the "ancient scent" still hung in the air!
The Baths of Diocletian also features artifacts recovered from other sites around Rome. Most noteworthy are the few Egyptian artifacts found here!
The Spanish Steps is only two stops away from the Repubblica - Teatro Opera metro station. You have to get down at, you guessed right, Spagna metro station! Unfortunately, the church had closed by the time I got there (6.30pm) so make sure that you go earlier if you want to visit the church too! This is another crowded tourist spot, so be prepared to jostle for space with many tourists!
After this, I returned back to the hotel. However, if you still have the energy, go for the "Colosseum by Night" tour that I talked about! I have read many reviews that raved about this trip! You will thank me later :-)
Day 2 was off to another auspicious start - a visit to Vatican City. Again, there is a "Skip the line" ticket, which you can purchase from the official website at a lower fee. I spent about 3 hours here (36 hours only in Rome, remember? ;-) ). So, to be honest, I could not complete everything. Ideally, the Vatican requires one full day - you come in at 8 and you leave at 3pm (or whenever it closes).
Do not miss the Sistine Chapel, which is famous for the paintings of Michelangelo! (Fun fact - did you know that Michelangelo was actually a sculptor and not a painter?) After you come out through the exit, head over to St. Peter's Basilica. It is a gigantic chapel, with beautiful paintings and relics!
Before you exit the Vatican City, take a good look at the Pontifical Swiss Guards, who are the Pope's personal bodyguards!
If you are a geek, here is something that you should try - head over to the Post Office at the Vatican City (it is in a caravan to the right of the Basilica) and send a postcard addressed to yourself! I got mine after 2 weeks and it was so cool!
After the Vatican City, take the metro from the Ottaviano metro station to Circo Massimo metro station. First stop is the Circus Maximus. If you have the time, you can walk around the entire length of the track and visit a few monument nearby.
From the Circus Maximus, I walked down to the Baths of Caracalla. The Baths of Caracalla, named after the Emperor Caracalla, are better preserved than the Baths of Diocletian. You must visit this place if you buy the Archaeological Pass. This is only a few minutes' walk down from the Circo Massimo metro station, along the Viale delle Terme di Caracalla. Once again, there are hardly any crowds here, so the lush gardens be a nice photo-shoot op for you!
From the Baths of Caracalla, board the 118 bus to go to Appia-Bisignano. This is where you will visit the Villa dei Quintili, one of the most under-appreciated and yet, the most scenic monument in Rome! The entrance ticket to this villa was also included in my Archeologia Card.
I was awed by the scenery around me as well as the sheer magnificence of this site. If you truly are a history buff, you will enjoy the opportunity to touch-and-feel (literally!) the walls, mosaic flooring and other artifacts that are preserved in this site!
If you can make the 1-km walk to point H, Grande Ninfeo, you can see the via Appia Antica, still preserved in its ancient form!
Finally, it was time for me to bid adieu to Rome. I made a brisk walk to the stop, took the 118 and got down at Circo Massimo.
Things to see on Day 2, if you have more time - 1. Cecilia Metella, 2. The Catacombs of San Callisto, 3. Pyramid of Casius Cestius (yes, Rome has a pyramid too! Albeit, a shorter one than its Egyptian counterparts!)