The hip hop mogul was spotted cruising around town Thursday in the Magic City -- apparently wanting to stretch his legs and get a little exercise ... because he was on a bicycle and pedaling away along what appears to be an expressway of some sort.

We're told Diddy ended up pedaling his way on down to South Beach -- not far from his Star Island homes -- and yes ... he was all by his lonesome, just a man and his thoughts.

He was smiling at one point as well, flashing a peace sign ... and looking relatively happy for the trip -- but the fact he was out at all is telling, as it's just further evidence that he's apparently not all that worried about what's going on big picture.

Of course, we're referring to the two raids his homes were subject to -- which are part of a larger federal investigation against ... which is digging into claims of sex trafficking, etc.

Diddy hasn't been arrested, nor has he been charged ... and he's kinda flaunting that here.

Ya gotta imagine he's somewhat stressed out considering the probe is ongoing -- and if he is, you could argue this is Diddy trying to blow off some steam. In any case ... the saga is far from over -- and while he's under a microscope, he does have some folks in his corner.

As we reported, his pal Stevie J posted a video that showed off what Puff's parties look like from the inside -- highlighting the fact it's star-studded, and full of nothing but good times.

Fact is ... we know Diddy has thrown extravagant parties for years now -- that's kinda his rep in showbiz, and has been even before he became famous way back in the '90s. And, just like Stevie J implied ... tons of celebs have always flocked to his shindigs, A-listers included.

That's why it's a bit surprising to see so many on the sideline right now -- but perhaps it's to be expected. Frankly, the allegations against him are incredibly serious ... even though Diddy has vehemently denied all of them, and has called this investigation a witch hunt.