Castles

Ann, Are you asking for a guide recommendation?

Not sure what the question is here. If you already have a guide and you are asking about trains, there are TER trains to Blois departing from Gare Austerlitz. There are TGVs departing from Gare Montparnasse to St Pierre des Corps, you would then need to backtrack on a local TER to Blois.

If you are asking about guides in general to drive your group to visit châteaux, I would take the TGV to Tours Centre, there is generally an early departure from Gare Montparnasse, walk across the street to the Tours Office de Tourisme from where the tours depart:

https://www.tours-tourisme.fr/recherche/?q=minibus%20tours

If you just want to visit a few châteaux from Blois, the Château Blois would be an excellent start. There is public transportation (bus) to Château Chambord, and you can easily take a local train to Amboise to visit the two châteaux there along with the Clos Lucé.

I would also be curious if you're speaking of fortified defensive castles (châteaux), such as those in Fougères or Angers or opulent hunting lodges/châteaux such as those along the stretch of the Loire River near Tours.

I ask because the word "castle" (château) in French is used for many different things. A water tower, for example, is a château d'eau.

If you want to go from Paris to Blois, it can be done by public transport.

Take the train Paris to Orleans, where you transfer to a regional train to Blois. A bus from Blois train station takes you to Chambord.

anncruik,
Could you please clarify your question?