Rome

At approx 2km its about a 30 minute walk.
For a first timer it's a no brainer - close to the Pantheon, Piazza Navona, Campo de Fiori.
Here you will be roughly half way between St Peters and the Colosseum.

I agree with the previous poster. Some things are outside that 15-minute area, but you can take a number of buses or a taxi (inexpensive, go to taxi stand).

You can use Google Maps Directions - Pedestrian mode for any other questions like this. Add time to the Google estimate, because their times are based on very purposeful walking without slowing down to enjoy any of the many sights along the way.

There will be "major" attractions outside of a 15-minute walk anywhere at all in Rome so more important will be an accommodation which suits your budget and desired list of amenities (i.e. air conditioning; room size; elevator; terrace; view; soundproofing; credit card payment; etc.) The 'best' question has been discussed here at length, and we all have our favorite areas for different reasons. For instance, my husband and I are walkers who do not like buses/trams, and prefer to avoid taxis but we're willing to jump the metro once in awhile to save time so being closer rather than farther away from a station influences our choice.

Some of us like accommodations within walking distance of Termini - which feels plenty 'central' to us, with good access to both metro lines - and others prefer neighborhoods around Piazza Navona or in Trastevere. We've even stayed up in Prati, enjoyed it very much for its residential feel, and did not mind that it was a long walk to attractions on the south side of the city center. And walk we did even though there was a metro station just a block or so away.

There is no single area that will put you close to all the sites in Rome. The Vatican, Colosseum and Borghese gallery are all between 2.2 and 2.8 miles from each other, so at least a 40 to 60 minute walk. If you stay in or near the piazza navona it's about a half hour walk to the Vatican area and about at 45 minute walk to the colosseum. Same for the Borghese gallery.

You can always take public transportation but that can take just as long with the traffic.

Donna

I think its about 40 min walk. Its hard to estimate times because everywhere we walked we found a million places to stop on the way!! We stayed one minute from Campo Di Fiori and loved it. Walked down and got fruit at the markets each morning, lovely bakery and lots of coffee shops for breakfast.We didn't take public transport at all and a taxi once when it was raining. (It may also depend on your time contrainsts) We had sore feet but loved the walking. 30-40 to colloseum/ Forum, 15-20 to Vatican, 10 to Piazza Navona, 15 to Pantheon, 20 min to Trevi Fountain, 30-40 to Spanish Steps. I am very unfit but loved walking to all the things that interested me. I am not particularly into art, more of a history person, so there maybe other interesting things to other people that were further away, but we saw everything on our to do list by walking in 6 days.

Kglessner,

You can just open up google maps and put in your start/end destination and then click the "walking" icon and it'll give you a route + estimated time.

You can get an idea here: http://www.freemaptools.com/radius-around-point.htm 5 km/hr is a reasonable estimate of walking speed.