First of all, it was a nice experience using the funicular going up the hill. I thought it was very nice that if you buy a 1/3-day transport ticket, you can use funicular with no extra cost (as it is a part of the same transport system). The Petrin Tower is located on the top of the Petrin Hill in Mala Strana area of the city. It was a landmark built in 1891 and is built to resemble the Eiffel Tower. It is very popular among younger visitors to the Petrin Hill (I was there a little while and always lines of youngsters). I spent about roughly 45 minutes walking up the top of the hill (as an old man) and I have no desire to walk up the tower to see the city. I see plenty from the path walking up. If you thrill is to climb up 299 stairs step, this might be a worthwhile for you. As for me, there are other things to see on the ground when you are on top of the hill.
To visit the park where the tower is located you can use your bus/tram ticket. Beautiful park, flower gardens and views of Prague, you can relax and walk around during the afternoon or early morning. To visit the tower is a minimal charge and you can go up on an elevator, only a few people in line and after the ride to the top you can relax at the cafe for a delicious piece of cake and coffee or ice cream. Relaxing site to visit.
The tower is easily reached using the funicular railway but be prepared for queues. We got entry for free with the Prague Pass but there is the option to pay to use the lift which we immediately did. The views are fantastic and the staff are very friendly and speak great English. It can be very crowded at the top and the tower rocks slightly in the wind but this didn't cause us any problems.
We decided to use the lift to get to the top (as it was already an evening after a long walking day). The area at the top is quite small, so I imagine it may get very busy at some times. From the top, you can admire the views of the whole Prague.
Take the stairs, don't be sad and pay the 60czk for the elevator. Watch which door you take (one stair up and one stair down...as we found out to our cost) Part way up there is an open gallery which is nice then up you go to the top which is enclosed and on a hot sunny day with lots of tourists becomes a greenhouse. Take your pictures and get the hell out of there.
Climbing the 299 steps is well worth it to appreciate the wonderful architecture of the tower and see the fantastic views.
Entrance is CZK 150 and it would cost an extra CZK 60 for anyone wanting to take the lift.
The stairs are really well designed with separate up and down sets. There is a viewing platform about a third of the way up. This is where the idiots who can't follow a very large arrow, try to use the down stairs to climb up!
Because the construction of the tower is metalwork, the stairs are open to get some great views and enjoy the cooling breeze as well.
The views from the top observation area are stunning. The observation area is enclosed, but some of the windows are opened making it great for photos.
For those people who are apprehensive about heights, having glass around the viewing area would be a benefit
There are different ways to reach the tower including a funicular railway. We walked up past the castle and there is a great path to the tower.
Overall, this is an interesting place to visit but I wouldn't call it a 'must'. You can get pretty decent panoramic views from the castle as well (although, not 360).