I just returned from a week in Rome with my wife and 2 kids. First, the weather in February was delightful. The mornings were a crisp high 40s, and by late morning/lunchtime, the temps were 58 - 59 degrees F. A couple of days we didn't even bring our coats, just layered up with a shirt and sweater. One complete rain out one morning, luckily we were booked for the Vatican Museums at 8am, so we didn't have to deal with being outside.
Anyway, I booked tickets for us to visit the Colosseum with Entry to the Attic. These cost 24 euro per adult, I think our kids were free of charge. This was by far the highlight of our trip.
Thanks to a lot of great info on this forum, I figured out that the tickets for this go on sale 30 days in advance. The ticket booking slots are in 20 minute increments. So the first booking is at 8:50am, then 9:10am, then 9:30am and so on, all day. I also learned from this forum that the time that the tickets go on sale coincides with the exact entry time that you are trying to book. So if you want 8:50am tickets, they will be released for sale at 8:50am (Rome local time), 30 days in advance. For us Americans, this involves getting up in the middle of the night to book, but it's well worth it.
I do not know how many tickets are sold in each time slot, but I don't think it's very many. I'll explain more below.
I wanted to book tickets for Tue, Feb 11th for the earliest possible entry time in order to avoid excess crowds and lines. This meant that I was awake and on my laptop at 02:45am Eastern US Time 30 days before that. When 2:50 came, and the tickets for the 8:50 entry went on sale, I tried to get them, but alas, they sold out almost right away. So, I had to kill 20 minutes, and when the next time slot went on sale, I was able to get them. So I had 4 tickets (2 adult, 2 kids) for entry at 9:10am! You need to enter the name of each person which will be on the ticket, be sure to bring ID for everyone when you go to the Colosseum.
We got there early to take some photos and walk around, and around 9:00am decided to see if they would let us in early, and that was no problem. You enter through the security and then get your tickets scanned, and get pointed in the direction of access to the attic. Access is via a small elevator, it probably holds no more than 5-6 people including the person operating it.
There was no one in line for the elevator, we got right on and went up You exit on a level below the attic, but above the general admission crowds, there is not much of a view into the colosseum itself, but it's a great look at the inner tunnels of the upper levels, and a closer look at the 'mezzanine' level. You walk through some tunnels to some stairs, and take them up a couple of flights and emerge on the attic which is the uppermost level of the colosseum. The views of the forum, arches and surrounding area are great. Then you walk over and see the upper view of the entire colosseum and it's truly breathtaking, especially early in the morning.
The ticket and person who checked it told us we had 30 minutes maximum up there, but there was no one there supervising this. You could likely stay much longer if you wanted, we probably stayed up there for an hour.
The absolute best part was, during our hour up there, there was no more than 7 other people up there the entire time. We literally had the entire attic to ourselves.
This is a HUGE contrast to when we descended in the elevator to join the masses for the remainder of our walk around the rest of the main areas. There were literally hundreds of people at every possible view point where you would want to try to take a photo or just enjoy the view. We didn't have to sweat that at all since we already had the best view and took great photos with NO ONE in the background.
I had been wavering on the attic vs. the underground tickets. It's a no brainer, the attic is the winner.