I had a couple of instances at the Rose Series event with balls lying in a Penalty Area but also close to an Immovable Obstruction. The photo below shows the first one.
As you can see, this young lady’s ball ended up on the bridge across the ditch just short of the second green (which you can just see on the right of the photo). As the ball was within the Penalty Area her only options were to play it as it lies on the bridge, or to take Penalty Area relief under Rule 17. If she had been left handed it would have been fairly easy to play it where it was and she would have been grateful for her good fortune. Unfortunately as a right handed player it was so close to the edge of the bridge that there was nowhere to stand. She made the sensible decision to take back on the line relief (despite her caddy trying to persuade her to play it) and was left ruing the hard bounce that her got her there.
If you have sharp eyes you will also see a multiple LET winner in the background who had also ended up in this ditch after going for the green in two. She initially dropped back on line from where the ball was lying in the ditch, rather than using the correct reference point (where the ball last crossed into the penalty area). Thankfully I checked with her before she had played so she could drop in the correct place (and get a marginally easier shot) without incurring any further penalty for playing from the wrong place.