Actually, it seems to be a folly from the 18th century:
More than £1 million of restoration work will be needed to return a historic monument to its former glory after decades of vandalism has taken its toll.
The Temple of Theseus has been virtually concealed within woodland inside the grounds of Hagley Hall, near Stourbridge.
The building pays homage to an ancient Greek temple built in 449 B.C. in the country’s capital Athens.
Generations of visitors were able to marvel at the brick and stone-built temple during visits to 350-acre Hagley Park.
But after the A456 Birmingham Road was built, the temple became separated from the main Hagley Hall, leaving it at the mercy of vandals.
The site has been closed to the public for a number of years in a bid to halt the vandal attacks.
Huge gaping holes in the building’s ceiling, where plaster has broken away, reveal exposed roof beams.Unsightly graffiti has been daubed around walls inside the building which has now had mesh-metal fencing put around it.
The Grade-I listed building was built around the 1750s close to the time when the 63ft Wychbury Obelisk was constructed.
Lord Cobham, Christopher Charles Lyttelton, who owns Hagley Hall and Park, says his family has worked closely with English Heritage who may provide some of the funding for the works on the temple.
“It is a shame it has got into this state,” he said. “We were unable to keep it secure and I believe it became a bit of a hangout for people.
“I’m sure it will cost at least a million pounds to get it back to something like it was.”
The estate is waiting to hear if an application for more than £1 million worth of funding for works on Hagley Hall itself has been successful.
The original hall roof was destroyed in 1925.
via Restoring temple to cost £1m | Express & Star.
There’s a bit more info on this and associated follies in the Hagley Hall Wikipedia page …