The feature was designed to look like Cleopatra’s needle – but designers added four small spheres at the bottom of the sandstone structure.
Residents and dog walkers say it gives the monolith an unfortunate phallic appearance and silhouette.
Workers put the finishing touches on the pillar in Betts Park, near Penge, in south east London, on Thursday.
Local office worker Sam Vale, 42, walks in the small, 13-acre park twice a day with her dog.
She said: “I can’t stop shaking my head and laughing at it.
“An obelisk going on the plinth is a bit weird, but fine, I suppose, but it wasn’t a good idea to put balls at the bottom.
“They weren’t on the original plan, otherwise I might have politely suggested they be removed.
“I don’t mind them doing up the park, but I’d rather they spruced up the signs and benches, rather than giving everyone something to gawp at.
“You really couldn’t make it up.
“Luckily, I can’t see it from my bedroom window, but I know others who can, and they’re less than impressed by the size of it.”
The obelisk, officially named the ‘Heart of Anerley’, was constructed to celebrate 200 years since the foundation of Anerley, an area in the borough of Bromley.
It was built on top of an existing plinth that originally held a sundial, and proudly stands almost 20ft (5.85m) tall, in the middle of the historic park, which also contains the last remaining section of the Croydon Canal.
The obelisk was organised by local community group Friends of Betts Park, who originally lodged plans last year.
During the planning phase of the project, only one local objected to the council.
They wrote: “What on Earth are they thinking of?
“The park is an open space of natural beauty in the midst of a concrete jungle.
“The last thing it needs is more concrete imposed on it, never mind the greater environmental damage of producing and transporting a giant bit of concrete to a green open space.
“Madness.”
Alan Pottinger, Secretary of the Friends of Betts Park, said: ”Friends of Betts Park are thrilled to have been able to construct this obelisk in Betts Park, Anerley.
”It’s taken a lot of hard work and years of planning to create a focal point for our tiny town on the very edge of the London Borough of Bromley, overshadowed by the ruins of the Crystal Palace.
”The monument will soon be dedicated as Heart of Anerley with its purpose being to celebrate the bicentenary of Anerley in 2027, and be a permanent equitable memorial to everyone whose names never get written on monuments.
”Friends of Betts Park will continue working hard with Anerley Town Hall and local councillors to regenerate our special corner of London.
”If persons on social media wish to remember the obelisk as phallic then we have achieved our goal of being noticed and remembered.
”Anyone is welcome to visit and there are guided tours in June as part of the London Festival of Architecture https://friendsofbettspark.eventbrite.co.uk.”
