It is the truth that non-Muslims are not allowed in the holy city of Mecca but there is no restriction for the common people to visit the city Madinah. Non-Muslim entering the Nawabi Square where Al-Masjid Al- Nawabi is located is prohibited. The reason for the prohibition lies between the fundamental requirements and the policies of Saudi Arabia. If any non-Muslim try to enter into the Mecca it will lead to some kind of penalty as well as lead to punishment.
As Mecca is the holiest shrine so some of the important elements are there those have to be kept in mind before entering. One should be a believer. For example, as civilians cannot enter cantonment without having any special permit similarly if you are not a Muslim you cannot enter in there.
Mosques or any other holy places are actually reserved for meditation and for meditation it is required that you need to be clean and pure. Prayer is a very neat form of remembering your god because prayers and meditation requires a lot of cleanliness.
Although, it is also said that Muslims are also prohibited to enter the Mecca if they are not clean. But as there is no one to keep the eye to check this. But it is believed positively that they follow cleanliness guidelines before entering as there is mentioned a specific way to take bath so it is assumed that they must have followed the same procedure and therefore non-Muslims are unaware of it hence, they are not allowed to enter in Mecca.
There are two major events that happen in Saudi Arabia. One is Haj and other Eid Ramzan where the number of Muslims assembles together for the prayer. Saudi Arabian have own way of checking. For example, while driving from the highway of Mecca and Madinah; the guard can check the ID proof of the travelers if they have any suspicion on them. If they are non-Muslims they are turned around back.
We all must have a question in our mind what is exactly there at Mecca? Every Muslim who is fit as well as fine has to visit Mecca once in their lifetime. Also, it is a feeling of unity and togetherness in them keeping aside the status, color, economic.
There are different probation in Hinduism as well as Christianity. There are others such as Hinduism and Christianity who also says that no entry to people of a different faith. But one should respect all the rules and regulations because not following it sometimes takes you in trouble and they are made keeping in mind all the values.