Foreign Travel Advice of the British Foreign and Commonwealth Office

Map created by reddit user jesus_stalin, based FCO data, from 11th June 2015

The map above shows areas where The UK Foreign and Commonwealth Office (FCO) is advising people against all travel (red), against all but essential travel (yellow) or to see travel advice before travelling (green).

Like most foreign travel advisories, there are the expected and unexpected.

Expected places to avoid altogether include:

Syria and Northwestern Iraq (due to ISIS)
Most of Afghanistan and sections of Pakistan that border it.
Crimea
Yemen
Somalia
And large sections of central Africa due to crime, terrorism and health concerns.

Some slightly less expected places that you should avoid altogether include:

The border between India and Pakistan, except at Wagah
South-west Mindanao and the Sulu archipelago in the Philippines due to terrorist activity
All travel in Venezuela within 80km (50 miles) of the Colombian border.
Preah Vihear (Khaoi Pra Viharn in Thai) temple area and the Ta Krabey/Ta Moan temple area located on the Thai–Cambodian border due to the presence of troops in the area and the risk of outbreaks of fighting.
The exclusion zones around the Fukushima Dai-ichi nuclear facility in Japan.

Finally, there are a few places without express advisories against all or even essential travel that you might expect to find on the list:

North Korea
Any of Mexico, despite the ongoing Mexican Drug War.
United States due to its high crime rate, although to be fair using this criteria the FCO would also have to issue warnings about Brazil, Jamaica, South Africa, Argentina, Estonia and about 105 other countries/territories that have a higher murder rate than the US.

Note: The data above was accurate of 11th June 2015 but now may be inaccurate. For the latest advice please visit the Foreign travel advice section of GOV.UK.

Now to see how these compare to other countries consider the following maps.

France