AT LA DÉFENSE, Europe’s biggest purpose-built office complex, workers are putting the finishing touches to the Majunga Tower. The handsome 45-floor building (pictured) in the business district west of central Paris is due to open around August. There is only one drawback. The building, currently unlet, will add 63,000 square metres to a park where the vacancy rate already tops 12%. Another big building is scheduled to open in 2014.

Vacancy rates can improve quickly, argues Olivier Gérard, who runs the Paris office of Cushman and Wakefield, a property consultant: these are big spaces for big clients, and relatively few leases will fill a building when firms feel more confident about the future. But only a few strides across La Défense’s wind-whipped main drag, the area’s biggest office block, Coeur Défense, fleetingly owned by now-defunct Lehman Brothers, is being sold again by its financially troubled current owners for a reported €1.3 billion ($1.8 billion) to an American investment outfit, Lone Star.

La Défense epitomises a paradox about Europe’s commercial-property market: a new boom has begun before the previous bust has ended. To generalise broadly across a wide range of property and economies, the mismatch between investors’ enthusiasm and the caution of occupiers has rarely seemed bigger. Investment is pouring back in (see chart), but tenants are not. Outside Britain, Ireland and Germany prime office rents were weak in 2013, says Knight Frank, another consultant.

Promising, but empty It is rock-bottom yields on government bonds that have nudged investors toward property. As the price of prime assets rises and growth prospects brighten, some are moving into second-tier cities, dicier properties and recovering basket-case countries. The buyers are taking a gamble that economies will liven up enough to fill buildings with paying tenants. France has attracted less investment than Britain or Germany, where economic growth looks steadier, and has seen a smaller proportional increase than Ireland or Spain, which promise assets on the cheap. But even in the robust German market there are signs that the bust is not over. Creditors of IVG, once Germany’s largest property company, voted on March 20th to take over the firm in a court-supervised plan to restructure its $3.2 billion of debt. IVG also agreed to sell its asset-management business, which manages a fund that owns half of London’s “Gherkin” tower. It was another building, though, that tripped up IVG, already wobbly from the effects of the financial crisis. Construction costs spiralled on the Squaire, a complex built on top of the railway station that serves Frankfurt’s airport. Tenants groused, vacancy rates were high. Overindebted IVG struggled to pay its debts. Germany can shrug at this cautionary tale, though. DG Hyp, a bank, says rents grew by 3.2% in seven “prime” cities in 2013 and by 2.3% in smaller centres—a strong result, given GDP growth modestly above zero. New jobs, especially for office-workers, are driving demand for space. Vacancies are declining, as there has not (yet) been a boost in new building.

Investors in property markets farther south are also drawn by relatively attractive yields (the ratio of rental income to the price of a building). But the worst of Spain’s economic nightmare may be over, which bodes well for prices, whereas for France the gloom seems unending.

Prices in Spain have fallen by 30-40% from their peak and many think they are now near the bottom. Investors are swarming over the capital, looking for bargains and betting on a (still shaky) economic recovery.

Banks with dubious property portfolios have been selling their real-estate management arms to private-equity firms. Spain’s “bad bank”, set up in 2012 to house €51 billion of troubled property assets, began offloading them in 2013. Amancio Ortega, founder of Zara, a big fashion retailer, has snapped up sites in Barcelona and Valencia. Investors bought over €3 billion-worth of commercial property in 2013, up 60% on 2012. This year they piled into two new real-estate funds, with hedge-fund titans George Soros and John Paulson both taking stakes, along with a Dutch pension fund, APG. Banco Santander is close to selling one of Madrid’s most famous buildings, Edificio España, to a Chinese investor. For many, Spain is the European commercial-property story of 2014.

France has less to cheer about, but optimists note that the gap between yields on property and those on government securities is the highest in 20 years, which should underpin prices. That bet will pay off as long as growth is not too feeble, interest rates do not rise too fast and the supply of new space does not swamp demand. No country in Europe can afford too many empty buildings.