THIS week one of Oxfordshire's most expensive homes went on sale for £10million. 

But if that's small change for you, how about doubling the  price and building a palace for yourself?

Currently, it is a vast green space, but someday soon it could be the site of a mega-mansion.

Land (pictured below) with permission to create Britain’s largest new home has gone on the market – but it will set you back £20 million.

St Johns House could one day be a 68,000ft mega-mansion with more than 80 rooms and the equivalent floor space as 60 average family dwellings.

It boasts an enormous master suite occupying the entire top floor, a grand ballroom and even an underground car museum to house 50 exotic motors.

We've had a look for some more amazing millionaire pads in Oxfordshire - here they are

Oxford Mail:

Oxford Mail:

But at the moment it is just a plot of land with a large stone barn on the edge of the village of Ramsden in Oxfordshire

Following a decade of work, planning permission was granted for the Palladian-style country house, which was designed by the world-renowned architect Robert Adam.

The indoor sports complex will have a swimming pool, gym which overlooks the ballroom, leisure room, prep kitchen, bowling alley and a jacuzzi, sauna and steam room.

The lavish entertaining floor, known as a 'Piano Nobile', has a formal dining room, music room, formal living room and games room which overlooks the orangery.

There will also be two gate houses, a self-contained guest gazebo, guest lodge and five bay garage.

Outside, the estate, which looks towards the Cotswolds, will have landscaped gardens, a tennis court and a second swimming pool.

Savills is now looking for a buyer to snap up the land and build the country home or another similarly-sized mansion.

The estate agent won't reveal the price of the site, but it is thought to be available for around £20 million.

If you want your mansion already built though, North Aston Estate is still on the market.

In 2014, a 77-acre plot of land near Windsor Great Park with permission to build a 33,000 sq/ft home was put on the market for £30 million.

If built to the approved plans, St John's House could be likened to Updown Court, the 15-year-old mansion in Windlesham, Surrey, which is also set in 60 acres but is 25 per cent smaller than the proposed Oxfordshire pile.

Charles Elsmore-Wickens, from Savills, said: "I am not sure if there is anything else currently like this with consent in the UK.

"It is in an elevated position with far-reaching views across the Cotswolds, an Area of Outstanding Natural Beauty.

"The house has been designed by a renowned architect, Robert Adam, who has created something unique and with a global appeal.

"It will be a stunning home to entertain in and you could keep a fleet of classic and supercars in the on-site museum.

"You could land your private jet at Oxford airport and then take a short helicopter ride the house. This really is an outstanding opportunity for someone to build the house of their dreams."

Mr Elsmore-Wickens added: "Finding a site like this and getting planning permission is very rare and it would be difficult to replicate it. It will be an extraordinary modern country house."

When completed, a house of this size and grandeur in a stunning rural location could potentially command an asking price of in excess of £60-70 million.

This could see a buyer having to fork out a further £8 million in stamp duty.

READ AGAIN: Reader reaction to £10million Oxford home

However, if the site is bought by an owner occupier, they will pay £2.3 million in tax based on a potential £20 million price. They would also be exempt from paying VAT on building materials because it is a new build.