5 things to know for your New Day -- Thursday, May 21

From the 1st to the 2nd century, the art and architecture of Palmyra, standing at the crossroads of several civilizations, married Graeco-Roman techniques with local traditions and Persian influences. The fabled desert oasis saw its last tourist in September 2011, six months after the Syrian uprising began. It is feared that the ancient city is now under threat from the ISIS militant group.

(CNN)ISIS takes over yet another city. Oil spill cleanup continues on the California coast. And David Letterman says goodbye and goodnight.

It's Thursday, and here are five things to know for your New Day:

ISIS

Another city falls: ISIS militants grabbed control of the Syrian city of Tadmur, which is close to the ancient ruins of Palmyra, a UNESCO World Heritage Site. ISIS controlled most of Tadmur by yesterday evening, after Syrian government forces fled to the city's security headquarters. Many fear that ISIS will destroy Palmyra's ruins, just like the militants destroyed the ancient city of Nimrud and took sledgehammers to statues in Iraq's Mosul Museum.
    ISIS' advance on Tadmur threatens UNESCO heritage site
    From the 1st to the 2nd century, the art and architecture of Palmyra, standing at the crossroads of several civilizations, married Graeco-Roman techniques with local traditions and Persian influences. The fabled desert oasis saw its last tourist in September 2011, six months after the Syrian uprising began. It is feared that the ancient city is now under threat from the ISIS militant group.

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    BIN LADEN

    Treasure trove: Osama bin Laden apparently did a lot of reading and writing during his final years spent hiding out in a compound in Pakistan. At least that's what the release yesterday of 103 documents -- taken during the May 2011 Navy SEAL raid that killed him -- seems to indicate. Bin Laden was still obsessed with killing Americans and urged other jihadist militants to abandon all but U.S.-related targets. At the same time bin Laden was focused on his family, exchanging letters with his many wives and children, and even expressing excitement about an upcoming wedding. The documents also hint at the size and nature of the bureaucracy of al Qaeda at the time and of the extensive digital library that bin Laden had assembled, a library that often included titles on terrorism by American think tanks.
    Osama bin Laden secrets revealed in new documents
    Osama bin Laden secrets revealed in new documents

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    CALIFORNIA OIL SPILL

    Cleanup begins: The ruptured pipeline near Santa Barbara may have spilled as much as 105,000 gallons of crude oil on the California coastline. That's the worst-case scenario estimate from Houston-based Plains All American Pipeline, the company that owns the pipeline. An estimated 21,000 gallons made it into the Pacific Ocean. The cause of the spill is not yet known, but there were problems reported Tuesday morning at a pair of pump stations.
    This is what California's oil spill looks like
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    SOUTH CHINA SEA

    'Please go away': That's what the Chinese navy told a U.S. surveillance plane yesterday, as the plane flew over islands in the South China Sea that China is using to extend its zone of influence. The series of man-made islands and the massive Chinese military build-up on them have alarmed the Pentagon, which is carrying out the surveillance flights in order to make clear the U.S. does not recognize China's territorial claims. The Chinese navy issued eight warnings to the plane; the American pilots told them the plane was flying through international airspace.
    High stakes surveillance over the South China Sea
    High stakes surveillance over the South China Sea

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    RAND PAUL

    NSA 'filibuster': Paul did it again. Two years after his 13-hour drone policy filibuster, the Kentucky senator and 2016 GOP presidential candidate took over the Senate floor yesterday afternoon to rail against the NSA. The Senate is considering reauthorizing the section of the Patriot Act that involves the NSA's bulk collection of phone metadata on millions of Americans. Paul slammed the collecting of the phone records, calling it symptomatic of a bullying, out-of-control government. Paul spoke for 10 hours, ending his unofficial "filibuster" just before midnight Eastern time.

    Those are your five biggies for the day. Here are a few others that are brewing and have the Internet buzzing.

    Goodbye, Dave: David Letterman's final "Late Show," was sweet, funny and star-studded. Check out the highlights.
    Top moments from David Letterman finale
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    Motorcycle surfing: Who needs a surfboard and open water when you have a bike and open road?
    Beautiful: 100 years of Filipino beauty in a little over a minute.
    Baby meets avocado: A baby gets introduced to avocados, but don't count on her becoming a fan.
    Mom!: Mom does a face plant in the sand during daughter's proposal.