I last visited Berlin 20 years ago, in the summer of 1990. My wife and I traveled through newly ex-communist Poland, Hungary, both halves of the soon to be disunited Czechoslovakia, and East Germany. I extracted my own paint-tinted block from the still standing Berlin Wall with a hammer and chisel.

Back then, Berlin was two cities with a kill-zone in between. We visited the east during the day, but spent our nights in the west: At the mid-point of the trip, after having gone two long weeks without a decent cup of coffee, with two weeks more to go, a respite of capitalist indulgence seemed called for.

Berlin remains two cities. Those with money to spend continue to live well west of the dismantled Wall, in comfortable-to-grand wooded suburbs. To the far east of the wall are the grittier residential neighborhoods of the former east, ringed by the grim high-rises of the Communist-built satellite cities. Between middle-class Dahlem in the west and skinhead Hellersdorf in the east stretches a distance of almost 30 kilometers.

There is more than suffering in our ancestors' European past.

About midway between these extremities, what was once empty central Berlin has been rebuilt into a curious new tourist town, crammed with museums, government buildings, office towers, gleaming embassies, restaurants and hotels: everything for which a city could wish, except for actual residents. Whole streetscapes have been rebuilt, an amazing new infrastructure summoned to life. Walk those streets after closing time, and your footsteps will be your only company.

The achievement is no less amazing for being incomplete. Postwar reconstruction takes time, and Berlin is reconstructing from two wars at once: the destruction of World War II and the deformation of the Cold War. The Berlin palace of the Prussian kings was damaged in war, demolished by the Communists and replaced by their fake parliament building. That building in turn was demolished (it was deadly thick with asbestos) and in its place now stretches a vacant lot - over which, it is promised, a replica of the vanished palace will rise again. When? Who knows? Construction was scheduled to begin this year, but has been postponed to 2014 at the earliest, a casualty of the global recession.

Yet there is one work of reconstruction that is proceeding. We departed Berlin by rail for Poznan. (My sardonic 16 year-old son quipped: "Jews on a train heading east from Germany? That never ends well.") A century ago, these were the territories of the kingdom of Prussia, stretching toward Lithuana 700 kilometers away. Half a century ago, it was the fault line of the modern world, the designated battle ground of two vast nuclear-armed coalitions. Today? The border is open again. We boarded in Germany, exited in Poland - and never showed a passport. The highway alongside was thick with trucks carrying goods in each direction: a faster road is promised soon. Poznan has acquired a spanking new Porsche dealership.

What is being rebuilt is the world in which my forebears lived for I don't know how many generations; a world in which places like Bialystock and Lodz belong to Europe as much as Milan and Rouen do. Whether you are an American of Jewish or Polish or Ukrainian roots, you may envision Eastern Europe as a place in which your ancestors suffered and died. It was also a place where they lived - and in many cases, not only lived, but flourished. As the experience of catastrophe recedes, the memory of catastrophe is enriched by all that was not catastrophe. It's not only the future of Eastern Europe that is being rebuilt. It is also the past.