Just visited (July, 2015). Currently the cathedral is under restoration (scaffoldings hide rosette of main portal). Located nearby the Palace of Tau is closed on Mondays but it is possible to visit the Museum of Saint Remy (former Abbey of Saint Remy, also part of UNESCO heritage).

As in most of French churches the entrance to the cathedral (and St Remy basilica) is free of charge, although for the museum you should buy a ticket (if wanted to see interior of former abbey - worth visiting).