Thanks, they're beautiful!

Thanks mrsmel, very helpful

https://flic.kr/p/ABunZU
It's in the front garden of a house I just bought and I'd like to know if it is worth keeping. Otherwise I'm going to put…

Thanks. Have you seen them before? What is under the concrete thing? Did it used to have a big round tank half buried slightly downhill?

Picture here: https://flic.kr/p/xKtVCc
We're looking at buying a house and have no idea what the concrete thing in the backyard is. Is it something to do with…