From the Petite Tour, you can easily descend to the Col. Then, it is better to cross while keeping the summit on our left, going as easy as possible. Continue in this way almost to the end before seeing a wide and easy corridor which leads to the upper part of the Tower. You will then have to turn left to reach the summit cairn.
The ascent is quite easy, as is the descent, without ever approaching the void. However, it is better to have a little experience with this type of terrain (scree, route finding, etc.).
The view from above is magnificent, over Lake Allos of course and Mont Pelat but also over the other side as well as over the Petite Tour, an obligatory passage to go up to the Grande Tour on an easy hike.
To do if you are in the area!