Proudly proclaiming itself to be "the most participated sporting event in Italy," the Rome Marathon is very popular with both Italian and foreign athletes. Entry costs vary depending on how far in advance you register (see below), and further discounts are available for athletics clubs.
The 2017 Rome Marathon will be run on , starting and finishing in Via dei Fori Imperiali.
As well as the full marathon, the day also features a 5km fun run called the Roma Fun Run (or La Stracittadina), which is open to everybody for a small entry fee. Another option if you're looking for a shorter challenge is to look at the Roma-Ostia Half Marathon, which takes place a few weeks earlier, on 12th March.
The Rome Marathon starts and finishes on Via dei Fori Imperiali, working its way north to Pinciano and south to San Paolo. You can see the map of the 2016 route (we don't know what changes there might be in 2017) on Google Maps here.
Registration for the Marathon
Registration for the Rome Marathon is conducted through their dedicated website, and seems to get more complicated each year, with the exact rules changing depending on whether you're Italian or coming from abroad, whether you're a member of an IAAF-recognised organisation, and so on. Rather than trying to summarise everything here, your best bet is to head over to maratonadiroma.it for the rules, and then register at mymdr.it.
Registration fees vary according to how far in advance you register, and whether you're a member of an IAAF-affiliated organisation, so you could pay anything from €50 to €120 (though the deadline for the cheapest entries has now passed). The final deadline for registration is 15th March 2016 (with the possibility of picking up a bib until 23 March if they've not sold out), although you'll want to register as far in advance as possible to avoid any last-minute problems.
In the past, registration has been free for those competing in handbikes or wheelchairs, and for the blind. It's not yet clear what the situation will be for the 2017 marathon: the website above appears to have a section with information for disabled athletes, but the link isn't working. Check back nearer the time, or try emailing them at firstname.lastname@example.org