David F.
Google
Reading the name, I can assure you that you are expecting something different than what this museum actually displays. Sure, it was a palace at one point, but there isn't much left that would make you think it was. This is not a bad thing at all, as it is replaced with something just as great: a museum of the cathedral and the palace grounds.
The ground floor of the museum is all about the cathedral. It has a slew of busts, statues, and gargoyles recovered from the cathedral during excavations. They are very beautiful and are incredibly old. Several of them date back to 1270-1300, which is always really cool to see.
Upstairs is a small area dedicated to more about the cathedral and religious artifacts. There is a display of numerous models of the cathedral through time, which I liked. You could see its growth, downsize, and then growth again, to what it is today. There was also a display of colorized black-and-white pictures of the architects and workers who worked to renovate the cathedral. There were a lot of cool things about the pictures, and very interesting to see the pride many of them had in their reconstructions.
Downstairs, however, is the big event.
This area has artifacts from the archbishop, and the previously existing buildings on the site. There are coins from Holland and Germany (from trade), manuscripts, a broken archbishop staff, combs, buttons... I could go on and on about the stuff here. It covers an enormous area and is cool. You can spend a very sizable amount of time here, so be careful. Another cool thing about this area is that you can see the ruins of the castle, and later a mint. Only the bare foundations and the floor are remaining, but it was cool to see.