Not so long ago Salafis use to preach that travelling with intent to visit any other holy place or religious journey besides the three mosques, was forbidden. For example the Salafi fatwa:
it is not permissible to travel with the aim of visiting any holy place except these three. This does not mean that it is haraam to visit mosques in Muslim lands, because visiting them is prescribed and is mustahabb. Rather what is forbidden is setting out with that aim. If a person has another reason for travelling, and he happens to visit the mosque too, there is nothing wrong with that, rather he is obliged to pray Jumu’ah and prayers in congregation.
Times have changed and now we have official Saudi govt. authorized double decker buses and tourism packages to visit places ranging from Uhud mountain to the site of the Battle of Trench. The sites are currently few but its just a start.
Also see: Madinah ‘Tourist Bus’ runs pilot trip
Update (10/02/2018): Saudi Arabia to promote 250 ancient caves for tourism