About 270,000 people on Friday attended a Mass by Pope Benedict XVI in the same Warsaw square where his predecessor had inspired Poland's Solidarity movement against communist rule a quarter-century before.

The faithful filled the rain-drenched Pilsudski Square, standing resolutely in ponchos and under umbrellas. Church bells pealed as the pope was driven to the square through streets lined with cheering, waving people. An aide held an umbrella as Benedict ascended a high Mass platform topped by a 82-foot metal cross.

In his sermon, Benedict challenged moral relativism, or the view that there are no absolute values.

In remarks read in Polish by an aide, Benedict warned against those "seeking to falsify the Word of Christ and to remove from the Gospel those truths which in their view are too uncomfortable for modern man."

"They try to give the impression that everything is relative: even the truths of faith would depend on the historical situation and human evaluation," he said, in remarks that echoed his homily at John Paul II's funeral last year. "Yet the church cannot silence the spirit of truth."

Aneta Owczarek, 18, dripping wet without a raincoat, said she wouldn't consider going inside.

"No way," she said. "This is one of the most important events that could ever happen in Poland and we don't know if we'll ever see the pope here again."

Boy Scouts distributed tarpaulins to shield people against the rain, and people climbed on fences and sang along with the choir. Police spokesman Pawel Biedziak estimated the crowd at about 270,000.

That was less than in 1979, when some 300,000 people jammed the square, with some 750,000 in the surrounding streets, to see John Paul on his first trip to his native land as pope.

During that historic visit to what was then called Victory Square, John Paul challenged the atheist communist authorities, urging his people to "renew the face of this land."

Solidarity founder Lech Walesa would later credit the pope with energizing the emerging trade union resistance to Soviet-backed communist rule, which collapsed in 1989-90.

Benedict urged today's Poland — now a member of the European Union — to remain a strong Catholic voice in an increasingly secular Europe. "Stand firm in your faith, hand it down to your children," he said in his homily.

White and yellow Vatican flags festooned lampposts, and Benedict's picture stood in apartment windows; one window on Mazowiecka Street had pictures of both Benedict and John Paul.

"John Paul II was dearer to us, because he was our brother," said Barbara Kamela, 60, a retired bookkeeper who attended the 1979 Mass.

"This pope is visibly trying to be close to us, we have a strong impression from him and I came to this Mass to be near him."

The Mass is the highlight of the second day of a four-day trip that will include Benedict's trip to the Auschwitz-Birkenau concentration camp, a visit heavy with significance for Catholic-Jewish relations, a favorite cause of both Benedict and John Paul.