During history the Catholic Church has been given a great deal of miraculous incorruptible bodies of Saints. They just don't go trough normal decay after death, but stay the same. The oldest one that I have seen, is St. Silvanus who was martyred in 310 A.D. after getting his throat slid. He is still on display in Dubrovnik, Croatia and has been incorrupt for 1700 years!!
There was also such a miracle on Norwegian soil long time ago. An Irish princess, Sta Sunniva, that had come over by ship to the Norwegian island "Selja" and had been killed with her company in a landslide in a cave, while they were trying to escape from the hands of the local vikings, was found dead under some rocks about 30 years later. She looked like she was only sleeping, and the bones of those that were killed with her had a sweet fragrance. The King of Norway, Olav Tryggvason, had her relics put in a beautiful coffine in 996 A.D., and this miracle at Selja played an important part in the miracolous conversion of this barbaric nation of pirates from brutal paganism into Christianity.