Flat as a millpond

It is a millpond. The sea that Titanic sailed on was described as being like a millpond.

It's here at this old mansion I blipped before. The desmesne included a farm with its own mill to grind the corn. There was an upper pond to drive the waterwheel and this was the reservoir for the water that flowed through, used no doubt to supply the animals and the gardens. We have the recent weather to thank for the amount of water that the ponds currently holds.