Thorne Island, a private Welsh island with a 19th-century fortress, is now for sale for £3 million (around $4 million), according to the listing by Strutt & Parker.

Located three nautical miles from the Pembrokeshire coast in west Wales, United Kingdom, the island spans approximately 2.49 acres and is famous for its helipad, rooftop bar with a games room, and a majestic picturesque seaside office view.

The fortress was built between 1852 and 1854 as part of the outer defenses of Milford Haven, intended to guard against a Napoleonic invasion. Its military role eventually diminished, and in 1932 it was sold for the first time and converted into a hotel.

CNN reported that it originally accommodated 100 people. Today, its renovated facilities can host up to 20 guests in five cozy bedrooms, along with a luxury dining area and lounge spaces.

British tech entrepreneur Mike Conner, founder of Qodea and the island’s current owner, told CNN he bought it in 2017 for £500,000 ($670,000) after seeing it on YouTube.

"I saw it and it was just, 'Bam,' I wanted to buy it," he said.

The island is protected due to its Grade II listing, meaning it is recognized for its architectural and historical significance, with its design preserved. Conner was nevertheless thrilled to renovate the property.

He admitted he “underestimated a lot of things,” including the difficulty of installing flushing toilets, which required digging trenches through rock to enable a running water system.

Its construction is as hard as its fortress, as the materials had to be flown in with 350 helicopter trips over two days, and builders lived on the island for four years. Major works included sandblasting to restore the fortress’s original stone.

The overhaul, which cost more than £2 million ($2.7 million), was only completed this year.

Despite the challenges and long construction process, the 52-year-old owner said he enjoyed the journey and is already looking for his next adventure. “I’ve enjoyed the journey, and I think I would like to find another basket case,” he said.