I’m going to Italy in July and I’m wondering if I should purchase my tickets to the colleseum in advance? I know the lines get very long but I’ve heard you can buy a combined ticket there for the forum and collesum. My mom is worried they will sell out. Is that a possibility? Also are tickets required for the Vatican?
Tickets don't sell out for the colosseum, though if the colosseum reaches capacity they will hold the lines until enough people leave.
The entry tickets for the colosseum is a combo ticket which also includes entry to the forum/palatine hill. You have two consecutive days to visit these two sites with a single entry to each. If you wish to bypass the long ticket lines you should purchase entry tickets online. There are two different tickets, date/time specific tickets and "open" tickets. The open tickets are only valid after 2pm while the other tickets are time and date specific. If you wish to visit in the morning you'll need to get the timed tickets if they are still available. Book only through the official website.
https://www.coopculture.it/en/colosseo-e-shop.cfm
The "Vatican" is a city state with only a few areas being open to the public. If you with to visit the Vatican museums you should book entry tickets or a tour in advance in order to avoid the hours long lines. The basilica is free to enter but you'll wait in the security line for that as well. Book only from the official website:
https://biglietteriamusei.vatican.va/musei/tickets/do?weblang=en&do
Read through the different options to see if you want a tour or just entry tickets.
Donna