Tournai is a city in Wallonia.
Tournai is served by regular trains from all over Belgium From Brussels direct trains run every hour and take just under an hour. Direct trains run to Lille just across the border in France, which has a Eurostar Station. Trains take 30-60 minutes Paris is accesable with a change in just under two hours. See here for more details and timtables
From Brussels Coaches would take around 1h 45m and require 2 changes See here for timtables
The nearest Airport is Lille Lesquin which is served buy a few Budget Airlines heading to Milan, Warsaw, Leeds and Marrakesh The airports of Brussels, Charlroi and Paris would also be useful.
Tournai is fairly compact and can be easily covered on foot. There is a local bus service
It open 9am - 12 Midday 2pm-5pm (6pm in summer) Services 11am Weekdays 10am weekends
It is open the same times as the Cathedral, but closed on Mondays