Monaco is a mere mountainside sliver of 2 square kilometres. Its 36,000 people make it the most densely-populated place in the world. The city-state's heady mix of glamour, chic and wealth is hard to resist for people with money to spend or salt away. Demand for a piece of the action is high. For saturated Monaco the only way is up. Planning vital expansion is a constant trade-off between demolishing period properties and forcing locals out, and adding square metres. The principality's biggest challenge is growing. One study says we need to add around 350,000 square metres of useable space every decade. its surface area. So we are applying a an urban planning policy that ranges from extending into the sea, to rebuilding much higher on land," says Public Works, Environment and Urban Planning Minister Marie-Pierre Gramaglia. In 1965 Prince Rainier I launched Monaco's most ambitious land reclamation scheme, the Fontvielle district. Eight years and seven million cubic metres of rubble later the town had gained 15 football pitches worth of flat land. Monaco has enormous problems to overcome if it is to grow. When we build we have to do unusual things, underground and with coastal works. No country in the world has ever built what we will have to do in Monaco," says the principality's Consultant Engineer René Bouchet. He's worked on Monaco's most recent land reclamation project, the dyke that now protects Port Hercule from the waves. We had to forget the idea of a classical levee, because we had depths of 45 to 55 metres to deal with. We spent time to come up with an environmentally-responsible design for a marine location that would also absorb the shock of the waves where it posed a potential risk" he says. A semi-submersible concrete dyke made in Gibraltar was towed into Monaco in 2002. The visible part is only half the story. You have to descend four levels of car parks to find out how this part of Monaco is attached to the land. This is the impressive metallic articulation that fixes the dyke to the land. It can rock with the waves even in severe storms and disperse their energy into the landmass," adds Bochet. Monaco is not stopping here. A tender is out for a new extension. On land it is all about height, not depth. Like Hong Kong Monaco has learned to live with public lifts and escalators. Forty assisted routes compliment traditional stepped pavements. Architecture is so central to life there is even an expression, "France begins where the buildings stop." And in the 21st century architects are once again looking to go higher. When the Odeon Tower project is completed its 170m height will make it one of Europe's tallest buildings. Designed by a local architect, delivery of its units begins next summer. "The tower marks an architectural turning point for because we're going back to the high-rise buildings that the principality abandoned 20 years ago, but applying contemporary styles," says architect Alexandre Giraldi. Forty-nine floors will provide stunning views at a stunning price; between 40 and 90,000 euros the square metre. The pool-equipped penthouse will be the world's most expensive flat. The price is partially explained by the technological challenges building the Odeon, which began on day one with the breaking of soil in 2009. We had to scoop out virtually an entire mountain slope, and 70 metre-deep retaining walls is I think a record for a private-sector building. There is no unbuilt space in Monaco. Every time something new goes up, something must be demolished," says Giraldi. This perpetual renewal raises the question of how to preserve Monaco's heritage. New properties may be cutting-edge environmentally, but there is nostalgia for what's been sacrificed, too. The Head Conservationist at the New National Museum has spent two years reassembling Monaco's past, through photos. The Monacopolis exhibition is the result. You'd have to be very naive if you thought you could preserve Monaco's buildings eternally, as space is at a premium and we need more. But we might have to think about going to far one day. By building too high we might hide the mountain, and it's Monaco's mountain-sea location that makes it so beautiful, so desirable," says Nathalie Rostischer-Giordano. Monaco's most significant buildings are of course listed and protected. Prince Albert II is committed to examining each and every high-rise project, taking both the need for square metres and the risk to Monaco's charm into account . More about: Architecture, Environmental protection, Monaco, Prince Albert II of Monaco