Pools, trampolines, and so on: Great fun or tremendous work?

The spa that means relaxation to you may just say work to a buyer. Same with a pool, pond, trampoline, or some cricket nets. Some buyers see only additional upkeep and liability when these backyard “features” come into view.
Don’t put a pool in if you don’t have one. You won’t get the money back. If you do have an inground pool, it needs to be sparkling clean and in good repair.
If you have an aboveground pool or spa, your best bet is to remove it and clean, repair, or re-sow over the bare spot in the grass or deck. Same goes with a trampoline. Just as extra stuff eats up the space and equity in the interior of the house, these extras make the yard and outdoor living spaces look smaller.
Ponds and water features are more popular these days but don’t necessarily add equity to your property. If you have a portable water feature, remove it before listing your property.