One year ago this week, Miami Beach’s mayor and city manager held shovels and posed for pictures in a rejuvenated botanical garden blossoming just a short walk from their offices at city hall.

Looking back, it appears they were unwittingly celebrating a breath-taking monument to a new era of Miami Beach corruption, in which tainted contracts were reshaping the city under their noses.

According to police and prosecutors, the overhaul of the garden was completed by a shady contractor in bed with a senior city official who rigged the award of the $1.4 million contract. Former purchasing director Gus Lopez is believed to have received a piece of the action on that and more than a dozen other contracts during the past seven years.

Seawalls, bike paths and restrooms were all laid or built by contractors that together paid more than half a million to a consultant, who in turn gave roughly half to Lopez, according to a criminal affidavit. Other allegedly tainted contracts covered everything from security services and lawn care to food concessions.

Corruption is nothing new in South Florida’s glitziest community, a city that seems to have hanky-panky embedded in its DNA. In the ’20s, it was Prohibition-era speakeasies. In the ’30s and ’40s, when casinos were illicit, Beach Commissioner Art Childers owned one in Miami and the S&G Syndicate ran bookmaking operations from Miami Beach hotel tobacco stands and cabanas.

The Beach is where mobsters Al Capone and Meyer Lansky lived in their golden years and where Alex Daoud sold his votes to a local banker in the ’80s before he was shipped off to federal prison — after which he wrote a book bragging about his exploits.

Despite this dubious pedigree, interim City Manager Kathie Brooks this week called Lopez’s arrest a “low point in our city, particularly after the year we’ve had.”

The allegations against the city’s former purchasing director can’t be viewed with blinders. His arrest Monday comes as Miami Beach City Hall is still reeling from a year-plus of controversy. A sampler:

• The FBI in April arrested seven fire and code inspectors who were charged with shaking down a nightclub owner and running “sham” cocaine for undercover federal agents. At the time the arrests were announced, agents said their investigation would continue.

• The police department is still repairing an image damaged by former top brass’ relationships with Ponzi-schemer Nevin Shapiro, an ongoing probe into the questionable use of money by a police-related charity and the September arrest of a cop on racketeering charges related to a ring that used straw buyers to resell leased cars or secure bogus loans on cars that had already been bought and shipped overseas.

• Investigators began looking this month into a parking enforcement officer’s letter alleging that his supervisors were giving a free pass to the illegally parked cars of customers at iconic restaurants.

• Two city commissioners were under investigation until May, when a probe cleared them of colluding before a vote to fire the then-city manager, who himself had recently been cleared of trying to extort the New World Symphony.

Concerns linger that Lopez was looking to score big by rigging bids for Miami Beach’s ambitious convention center redevelopment project, the genesis of the investigation that led to his arrest Monday. Prosecutors said early this month that they had not found evidence “at this time” that bids were tainted, but would not comment on the convention center project Monday.