From Easter Monday to November 1, open every day from 1:00 pm to 4:30 pm.  
The entrance fee is: € 3, – per adult (children under 12 years free when accompanied)
Address: St. Bernardusstraat 24b, 6211HL 

Of course, a number of the fortifications can also be visited. The Maastricht Vestingstad Foundation staffs two locations. Below you will find the locations and opening hours:

Line of Dumoulin
The tour, both above ground and underground, in the Line of Dumoulin is held weekly on Saturday 10.30 am. 
The tour lasts approximately 1.30 hours and starts and ends in the bastion Holstein (Cabergerweg at the Meubelboulevard Pans car park). In the months of July and August, these guided tours are also weekly on Tuesdays and Thursdays, always at 10.30 am.
(Wooden gate, with blue sign “Linie van Dumoulin”).

Bastion Holstein – Bastion Waldeck
This long casemate tour takes place every month on the first Sunday of the month at 10:00 am and lasts approximately 3:30 am. This tour is also above and underground and starts in Bastion Holstein (Cabergerweg at the Meubelboulevard Pans car park) but ends in bastion Waldeck (Tongerseplein swimming pool Jekerdal). The museum of the 2nd World War and the Cold War in the Couvreface Wilcke is also visited. In the casemates there is a constant temperature of about 11 degrees, so do not forget to bring a sweater. Given the stairs and the inclines to be taken, both tours can only be done for guests with limited mobility.