A Remuera mansion - complete with a giant pool, four bedrooms, five bathrooms and sweeping Waitemata Harbour views - is thought to be Auckland's most expensive mansion sale of 2016. The $18 million sale of 13 Burwood Cres was recorded on March 10. The 1586sq m site with expansive harbour views has a modernist 780sq m house, built around 2010. The seller was WSC Trustee Ltd, owned by Aucklanders Warren and Sarah Couillault. Couillault is a finance specialist who in late May bought a share of Macquarie Private Wealth New Zealand. A rich American businessman is understood to have bought the modernist mansion. Couillault said the house was designed by Julian Guthrie of Godward Guthrie Architecture. "He did a great job. We loved living there. It was a beautiful family home which we developed and built with him over a few years and lived in for a while." Guthrie said the design was inspired by Auckland's war bunkers. "The requirement was for a large new family home maximising connection to the exterior spaces and views over Auckland harbour. To create connection to the terraces, pool and gardens, the living areas were all placed one level below street entry level. Entrance is a sequence of reveals and descents into the home. The house was inspired by the harbour edge war bunkers in Auckland, dug into the cliff while open to the sea." The Weekend Herald understands top agent Graham Wall was involved in the sale. Another exclusive clifftop property at 40 Selwyn Ave, Mission Bay, has been conditionally sold for $15 million in a deal yet to settle. The four-bedroom, two-bathroom home, with a fountain in its front gardens, also features a sweeping, formal circular driveway, mature gardens, unhindered Waitemata views, north-facing terrace dining areas and extensive native planting. Website homes.co.nz showed that an extremely large modernist house at 8 The Rise, St Heliers, fetched $11 million earlier this year. Jeremy O'Hanlon of homes.co.nz said: "The council record puts the size of the house at 706sq m, more than a typical section in Auckland's leafier suburbs." The six-bedroom four-bathroom property was advertised as "the pinnacle of modern luxury, a modern masterpiece boasting the best views of Rangitoto and beyond ... With its distinct art deco aesthetic, confident and classical concrete construction, positioned high above the glistening Waitemata, this home projects an air of permanence and dignity". Just this week, QV also released data showing national house prices shot up 5.6 per cent in the past three months, the fastest increase in the past 12 years. "The average value in Auckland now is $975,000 across the whole region. If the rate of growth increases as it is at the moment, we will have an average value of $1 million by 2017," said QV national spokeswoman Andrea Rush. Top agents are busy. One Auckland agent, Steve Koerber of Ray White Remuera, said on homes.co.nz that in the past 12 months alone he has sold 21 properties for $40.1 million.