If like me you like to see as much as possible in a destination, I would suggest going to the Tourist Office on arrival. There you can purchase a couple of town trails for about 2 Euros apiece - the Old Town Trail and the Fortifications Trail, both available in English, cover the Helpoort and take about an hour and a half each. They are a pleasant way to see a sight such as this, which is just an old monument otherwise! The Helpoort was actually one of the town gates to Maastricht, and the only one which survives. YOu can still see the grooves down which the gate came when the city needed to be locked each night. There is also an interesting structure on the fron of the gate, from where oil etc could be poured on the enemy. To the side of the gate, there is a small museum giving you more info, but like many museums, it was shut on a Monday which was the day we did the trail. There are other bits of wall nearby which the trail leaflet said were extremely pretty in the spring when bulbs come up through the remnants. If possible visit the Helpoort and then combine with a beer or a meal in the atmospheric Restaurant Sjiek, St Piterstraat 13, which is also deservedly highly recommended on Tripadvisor (reasonably priced too!)
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.