Toddler play equipment/small yard

Does anyone have any ideas what to get for the yard for my DS's to play with, they are 3 and 1.5 ?
There is only a small space for anything to go and also most of the yard is on a bit of a slope.

I don't drive and find it hard getting out of the house for most of the week so I need some interesting ideas for toys/play equipment.

I have thought of the obvious ones, sandpit, cubby, trucks.
I don't really want those small plastic playsets as the kids grow out of them to quickly and the plastic goes funny if outside all the time.

I just want to be able to send them outside and have them have fun and explore.

Ideas please ????

Those pop up tents with tunnel?
Shell pool with sand 1 side, balls the other?


Sent from my iPhone, more than likely while I should be doing something else!

I'm going to recommend the plastic play gyms - with the little slide/steps.
You can get them second hand on ebay for a pittance and our boys had a blast on theirs. They also used it as a cubby and put it under the line to help me hang out clothes.

A trampoline is usually a winner