I visited this WHS in Summer 2019. The Centennial Hall of Wroclaw or Hala Ludowa in Polish occupies quite a large part of the modern city of Wroclaw and the arena is capable of housing some 10,000 people. There are ample parking spaces just next to the hall or near the surrounding gardens but beware of the traffic on a hectic working day.

The Centennial Hall together with the Four Domes Pavilion, the Pergola, and the Iglica are a Polish National Monument. There 'uniqueness' or importance lies in the fact that they represent an early landmark of reinforced concrete architecture. On a sunny day, the stroll around the concrete structure and dancing water display with an ice-cream in hand was rather pleasant but the whole structure is not much of a sight to behold in my opinion. Although it was ahead of its time when built, most huge sports complexes nowadays have a similar structure and the same defect in my opinion - they might be functional but immediately after some years, their overall state and appearance easily turn shabby and ugly without constant painting and maintenance. 

There's a plastic UNESCO inscription plaque just by the entrance and photos of the metal ceiling from the inside which is the only thing to actually see but it won't make much of a difference in the overall impression. A similar experience can be had if you visit an indoor concert in a sports venue and look above. The majority of the people next to the Centennial Hall in Wroclaw were mostly visiting the park and the zoo nearby. All in all this is definitely one of Poland's dullest WHS.