Prague doesn't have much in the way of amusement parks. Given it's popularity as a holiday destination, I'd think setting up a city amusement park would be a pretty good investment. Something along the line of Weiner Prater in Vienna would be ideal.

It does have one area called Luna Park that's basically a small funfair, and not that great an example. when I've visited Prague it's always been shortly before Christmas so it's not been open. From what I've seen it's not really worth going out of your way for, but the Prague Aquarium in the same park and Prague Zoo nearby mean you do have a reason to be in the area.

If your looking for thrill rides in Prague this is what I'd recommend. It's a bit of the usual tourist trail, you need to get the Metro to a station called Palmovka, and from their get a bus two stops to a stop called Kelerka. There you should be right by the car park and entrance.

Being a bobsleigh there is some debate to if it's a roller coaster or not. I personally count full circuit ones like this as a roller coaster. This one consists of a huge layout, I had a look on Google maps and it takes up a plot of land approximately 300 metres by 60 metres. Unfortunately the first part of the ride feels like a bit of a waste as there's no steep strait at the start to give you an initial speed boost, so the first part of the ride is to mainly just gather momentum. Once you've got this momentum though the ride becomes a thrilling prospect, it can take a couple of goes to get used to breaking the cars. Once this has happened  you can tear around at a thrilling rate, and you do feel a genuine sense of danger as you gather speed coming in to some of the corners.

Another nice touch I should mention is at the end of the course they've put a speed trap. Don't worry you won't get any points on your licence, but you do get your speed displayed on a screen as you pass. This is a nice way of adding a challenging and competitive element to proceedings. It's something that will be on my itinerary on future trips to Prague.