I think it's probably the base for a shed/greenhouse or even a garage? Unless you really like hard work, I would do as the others suggest & lay new patio/reuse it as it is. It might be useful to work your way round the edge to see if you can work out how big it is, before getting a pneumatic drill out.
Sometimes, if you can dig under a slab, so the concrete is not resting on anything, then a good crack with a sledge will do the trick. Unless they've put rebar in
An electric angle grinder (whizzer) with a diamond cutting blade. Made short work of the five inch thick concrete pathway around my house. If the surface is thicker than the blade radius, cut as far as you can to weaken it, then attack it with the sledgehammer, assisted if needs be with hammer and chisel.
Angle grinders are very noisy, very messy, so wear ear defenders, eye protection, dust mask, thick trousers and stout boots (preferably with steel toecaps) and try not to work facing in a direction which will eject huge clouds of concrete dust into your neighbours' gardens. If at all unsure of how to use a grinder, get a builder or expert DIYer in. They can be very dangerous machines if not used in accordance with maker's instructions.
If it is an air raid shelter ( I once watched someone removing an Anderson shelter and it took all day using a petrol powered grinder/cutter and several men with hammers) you'll probably need help.
Thanks folks! That's all really helpful. It is in a slightly inconvenient place Vs where is like the new one to go, so Plan of attack, I think, is to try and dig down and find the bottom edge so I can be sure it's not the roof of something, then get someone in with a drill to get rid. Knew you'd hello me figure it out!
An old air raid shelter would not normally be made of concrete. It looks more like a foundation for something. Unfortunately nothing is going to grow on top of it. Looks like a job for a pneumatic drill.
We had a concrete air raid shelter in our garden that as kids we 'discovered'.After finding the entrance we had many happy hours playing in it.Once we lit a fire down there and we all struggled to get out of the tiny entrance together!!! Only children could fit through the small gap so no adults!
“Every day is ordinary, until it isn't.” - Bernard Cornwell-Death of Kings
We came across this in one of our gardens and it turned out to be a bomb shelter.Dig with caution as ours extended into the middle of the lawn,and it turned into a huge job.
The whole truth is an instrument that can only be played by an expert.
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Angle grinders are very noisy, very messy, so wear ear defenders, eye protection, dust mask, thick trousers and stout boots (preferably with steel toecaps) and try not to work facing in a direction which will eject huge clouds of concrete dust into your neighbours' gardens. If at all unsure of how to use a grinder, get a builder or expert DIYer in. They can be very dangerous machines if not used in accordance with maker's instructions.
If it is an air raid shelter ( I once watched someone removing an Anderson shelter and it took all day using a petrol powered grinder/cutter and several men with hammers) you'll probably need help.
Knew you'd hello me figure it out!