A PA 23 PILOT LANDED ON PBI TXWY L WHICH IS LONGER AND WIDER THAN THE ADJACENT RWY 9R/27L.

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UPON ARRIVING IN THE PBI AREA ON A FLT FROM THE BAHAMAS; I WAS INITIALLY CLRED FOR AN ILS APCH TO RWY 27R WITH A POSSIBLE SIDESTEP TO RWY 27L. I INTERCEPTED THE LOC APPROX 10-14 MI FROM TOUCHDOWN. AT APPROX 3-4 MI FROM TOUCHDOWN; TWR CLRED ME FOR A VISUAL APCH TO RWY 27L. I ASCERTAINED RWY 27L VISUALLY AND AT THE TIME THOUGHT TO MYSELF THAT IT WAS WELL MARKED; PROBABLY TO MAKE IT EASILY IDENTIFIABLE FOR PLTS. I ASCERTAINED THE VASI AND BEGAN ALIGNING THE AIRPLANE WITH RWY (RWY 27L); AND ON A SUITABLE GS USING THE VASI. AS I DREW NEARER TO RWY 27L I THOUGHT TO MYSELF THAT THE RWY MARKINGS LOOKED DIFFERENT; HVY AND BLACK; BUT AGAIN; PROBABLY TO HELP THE PLT PICK OUT RWY 27L DUE TO ITS UNUSUAL PHYSICAL LOCATION IN REF TO THE OTHER RWYS. AFTER BEING CLRED FOR THE VISUAL APCH TO RWY 27L; AND NO LONGER ASSIGNED RWY 27R FOR LNDG; I HEARD ATC GAVE A CLRNC TO AN AIRLINER. I WASN'T QUITE SURE OF THE EXACT CLRNC BUT WHAT I GOT WAS AIRLINER AND RWY 27R. I BEGAN MONITORING RWY 27R BECAUSE I KNEW IT WAS NONSTANDARD DISTANCE FROM RWY 27L AND I DID NOT WANT THE AIRLINER TAKING OFF INTO MY FLT PATH. THIS LED TO A PARTIAL DISTR OF MY ATTN TO THE JOB OF LNDG ON RWY 27L. WHILE CONTINUING TO WATCH FOR THE AIRLINER; I COMPLETED WHAT I THOUGHT WAS A NORMAL VISUAL APCH TO RWY 27L. I DID NOT REALIZE THAT I HAD LANDED ON THE TXWY UNTIL THE TWR ASKED ME WHERE I WAS GOING TO PARK. I TOLD HIM THAT I WANTED TO GO TO CUSTOMS AND ASKED HIM TO POINT ME IN THAT DIRECTION AS IT WAS MY FIRST TIME TO USE CUSTOMS AT PALM BEACH. HE SAID HE KNEW IT WAS MY FIRST TIME HERE BECAUSE I HAD LANDED ON THE TXWY. I TAXIED TO THE CUSTOMS RAMP AND WAS MET BY AN ARPT OFFICIAL WHO TOOK MY NAME; ADDRESS; AND PHONE NUMBER. HE TOLD ME THAT LNDGS ON THAT TXWY HAD BEEN A PROB AND THEY USUALLY HAVE 2-3 A MONTH. HE ALSO ASKED ME IF I HAD READ THE WORD 'TAXI;' WHICH WAS WRITTEN ON THE TXWY. (THIS ACCOUNTED FOR THE HVY; DARK MARKINGS.) I TOLD HIM I HAD NOT. I CLRED CUSTOMS AND CALLED ATC. THEY ASCERTAINED NAME; ADDRESS; TELEPHONE NUMBER; AND PLT LICENSE NUMBER. ATC ALSO SAID THAT LNDGS ON THAT TXWY WERE NOT UNCOMMON; AND IT HAD BEEN A PROB AT THE ARPT.