 If you turn off the M6, on the ragged edge of Preston, and follow some brown badger signs through a series of truck-filled roundabouts and ramps, you suddenly see a huddle of roofs above a lake, which look like a bronze-age settlement. The view recalls those meticulous yellow-brown reconstructions you get in old, earnest children's books, and you half expect to see men carrying spears and dead deer, and the smoke of a campfire.  It is in fact a brand-new visitor centre for the just-opened Brockholes nature reserve, and rather than spear-carriers you see citizens of local cities wearing sensible outdoor clothes. It is a complex of buildings with claims on the future rather than the distant past, in that it aims to be extraordinarily sustainable. and it floats.  Brockholes sits on a concrete raft, made buoyant by hollow chambers, held by four steel posts to stop it drifting across the lake. This is the building's way of dealing with flooding, to which the site is prone. It can rise up to three metres, which would only be necessary in a catastrophe, but will regularly go up and down by 400mm over a year. Whether we are immersed by the effects of climate change or simply persist in our fondness for building on flood plains, floating buildings might come to seem like a very good idea. "People have been in denial about flood risk," says the building's architect, adam Khan.  Brockholes is an overlap of wildness and industry. It has been formed over 10 years out of a former gravel quarry, with a range of habitats added to existing woodlands and water to "create a microcosm of what old Lancashire was like". It has been "carefully crafted" to attract different species and is aimed less at dedicated bird-watchers and nature lovers than the general public of the big cities an hour's drive or so away - Manchester, Liverpool, Leeds - and at tourists on their way to the nearby Lake District. The idea is to introduce people to nature who don't see enough of it.  Its buildings serve the usual needs of such places - cafe, shop, information - but also host a large education space and a series of conference rooms that will be rented out to generate income. Naturally, in such a place, they have to be scrupulously environmental, and so they are designed to achieve the "outstanding" category in the official measure of such things. (The British Research Establishment Environmental assessment Method, if you really want to know, or Breeam.) Until recently, buildings could only be "good" or "excellent"; Brockholes is on course to be the first building in its particular niche to achieve "outstanding", although the final judgment will not be made until it has been in use for a while.  Breeam concerns itself with everything from heating and ventilation to the height of light fixtures off the ground, to the sources of materials, the energy that goes into materials, their durability, their potential for recycling, and the distance they travel to the site.  Often, the pursuit of Breeam's approval leads buildings to pursue a box-ticking series of technical fixes, and an assembly of products designed to fulfil their requirements without much thought to how they look and feel. at Brockholes, adam Khan wanted to challenge this "factoid-led" approach, and use the pursuit of sustainability as the means to create more beautiful buildings, not less.  So he designed high, steep-pitched roofs enclosing large volumes (good for air circulation and extraction), clad in oak shakes - rough tiles formed out of tree stumps, which would otherwise be burned as waste. Gutters are in copper (long-life, recyclable), which adds a touch of luxury. Ventilation is entirely natural. The roofs are held up with timber beams made in a precise German process, and arrive on the site "as sharp as pencils". Insulation is a cheap but effective stuff made from recycled newspapers.  Then, charmingly, the building connects with its natural surroundings in a way that cannot be measured by technical indices. Because it floats, it has an intimacy with the water that it would lack if it were ringed with defences against flooding: the water is turned from an enemy into an ally. Reed beds have been planted around the building so that when they are fully grown the roofs will seem to emerge from them. From within, visitors will - in places - be able to look into the reeds, and into spaces carved out of them "like crop circles". In other places they will look onto open water.  The complex's buildings are arranged around a series of courtyards, which provide both a sense of enclosure and openness to views, and one of which is planted with a little orchard. The oak roofs change in the weather, from black in rain to gold in sun. Nor is it a matter of sight alone: t 