A water conduit head in Greenwich Park (at the north east foot of One Tree Hill), London.
Possibly built by Nicholas Hawksmoor there are inaccessible tunnels behind it.
Date: 1705 (?)
https://historicengland.org.uk/listing/the-list/list-entry/1393454
More info in this blog by Running Past: https://runner500.wordpress.com/tag/greenwich-hospital-standard-reservoir/
241 photos taken in November 2020 with a Sony a6000 and processed in Reality Capture.