BERLIN - One evening in the winter of 1961-62, a shuttered military train left Frankfurt, headed here through Communist East Germany.

The drawn curtains and sealed outer doors were meant to keep us - U.S. troops on weekend leave - from turning a childish prank (mooning, perhaps) into an international incident.

But at first light, I opened a curtain edge and, as the train slowed through a country town, I glimpsed the only person on the strangely barren platform: a teenager in a handsome tan overcoat with bright red piping along his lapels, a red star on his fur cap and an impressively ominous machine gun strapped across his chest.

My first Commie! My first Russki!

How could a return to Berlin, 46 years later, beat that?

By allowing me to roam the East Berlin that had been forbidden to U.S. troops in those dangerous days after the Berlin Wall began to rise in August 1961.

On my first full day in the former East Berlin, history slapped me. Hard.

No, not Checkpoint Charlie or any other memories of my brief time there.

It was Nazi history, starting with a hole in the air.

A block south of the Brandenburg Gate, across from the Tiergarten - Berlin's version of Manhattan's Central Park - was the Holocaust Memorial. An entire city block, empty at eye level. No high-rises. No buildings at all.

Only coffins. Rows and rows of concrete slabs: 2,711 of them. (The memorial's exhibit rooms are below the street.)

From all sides, the lanes between the slabs - slabs that I saw as coffins - dropped toward the center of the city block, so that people walking down a lane were well below the street - as if in the trenches, in the forests, where the Nazis mowed down prisoners.

I didn't choose to enter.

Memory would be enough.

I didn't map out a walking tour. I didn't buy advance tickets. I wanted to stroll the streets that had lived in my history books.

Past the U.S. Embassy, I walked north to the Brandenburg Gate, and turned east onto the tree-lined middle of Unter den Linden, the boulevard that runs straight from the Gate to the River Spree.

On a chilly autumn afternoon, rows of sidewalk tables outside Cafe Einstein were packed with folks warmed by sun and schlag - the cream that topped their coffee.

I needed to get to the cathedral - St. Hedwig's - to find the hours for Sunday Mass.