The main central areas of Beirut are Achrafiyeh (Gemmayze is part of Achrafiyeh), Hamra and Downtown. In all these areas you will find a diverse mix of people, lots of bars, cafes and restaurants and shops.
The areas surrounding Mar Mikhael, Gemmayze and Downtown, are quieter and often people will predominantly be from one religion or ethnicity. For example in Borj Hammoud you find Armenians; in Achrafiyeh and Roumanah – Christians; in Assass and Tariq al-Jadeedeh – Sunni Muslims; and in Dahiyeh and Basta – Shi’a Muslims. Some areas like Shiyyeh and Tayyouneh are more mixed – for example they have both Christians and Shi’a.
The Palestinian camps are also now quite mixed and in Sabra and Shatila there are many other migrants living there – Syrians, Asians and Africans.
Some areas of Beirut are definitely safer than others in terms of crime levels. Palestinian camps and Dahiyeh are not safe to go without a local guide. In particular in Dahiyeh, the locals are very sensitive to their security and it is not recommended that you visit without a local and DO NOT use your mobile phone or take pictures. If you are lucky enough to be shown around this area by a local, you will find that Dahiyeh is a vibrant area and the people you are introduced to will be welcoming and warm. Be aware that both the Palestinian camps and Dahiyeh are very overcrowded owing to the refugee situation and there is always the potential for a civil disturbance. In the past, these areas have also been the target of terrorist attacks, so it is very likely that your embassy will recommend you do not visit them.
However, overall Beirut is a safe city and in many areas you will not feel like an outsider.