Entry to Dubai for European citizens is simple and does not present any particular difficulties: a valid passport with a residual validity of at least six months is sufficient. Of course, the Arab Emirates being a country outside the European Union, it is not allowed to cross the border and enter the country with just an identity card.
Documents for visiting Dubai vary depending on the reason for the visit: for tourism, as mentioned above, there are no problems, and since 7 May 2015, a short-stay visa waiver (90 days for every 180) has come into effect for EU citizens who want to travel to Dubai or the entire United Arab Emirates.
A 90-day visa will be issued absolutely free of charge when entering Dubai or any point of entry to the UAE. Exceeding the time allowed within the country is strongly discouraged, as immigration laws in Dubai and throughout the UAE are very strict.
Should there be a need to stay within the territory for longer, it will be necessary to contact the consulate or embassy to find out the procedure to follow.
To recap, on arrival in the United Arab Emirates, European citizens can obtain a tourist visa valid for 90 days, so there is no need to apply before departure. After 90 days you must necessarily leave the country.
As far as documents to visit Dubai for citizens of other countries are concerned, UAE policy varies from country to country. Citizens of GCC (Gulf Cooperation Council) member states and, as already seen, EU citizens have no problem entering and leaving the country, while there are 12 countries whose citizens can obtain a visa on arrival valid for only 30 days: these are Australia, Brunei, Canada, Hong Kong, Ireland, Japan, Malaysia, New Zealand, Singapore, South Korea, the United Kingdom and the United States of America.
All citizens of other countries of the world, on the other hand, will have to apply for an entry visa to visit Dubai, which is obtained through a sponsor (practically every hotel in Dubai acts as a sponsor, alternatively, the airlines Air Arabia, Emirates, Etihad, Air Baltic, Air Serbia and flydubai can do this).
All you have to do is contact the hotel and they will take care of everything in exchange for a small fee for the service, alternatively, on the websites of the airlines listed above there is a special section for online visa applications.
You will need to provide details such as passport number, citizenship, reason for travel to Dubai or the UAE and date of return to your country of residence, and in a few days the visa will be sent by email, ready to be printed and presented at immigration control at Dubai airport.
City Card allow you to save on public transport and / or on the entrances to the main tourist attractions.