Kourtney Kardashian and Travis Barker Hold Hands in Portofino, Italy

Love has no bounds and no borders ... thus Kourtney Kardashian and Travis Barker continued their love fest in Italy.

Trav and Kourt were exploring the sites in Portofino as they walked hand in hand. They were both covered in large, almost-matching hoodies as they traversed the town.

This has been a super-romantic vacay for the 2 ... they've been exploring Italy in what is clearly a budding relationship. In fact, scratch budding ... it's full-blown at this point.

It's a huge moment for Travis, who just recently started flying again. As you know, he hasn't gotten on an airplane since the fatal crash 13 years ago that killed 4, including 2 of his close friends.

He flew for the first time a few weeks back when he, along with Kourtney, Kris Jenner and Corey Gamble, took Kylie's jet down to Cabo in Mexico.

The Cabo trip removed any doubt they are in a downright serious relationship ... making out in the main pool for all to see. The experience onboard a plane seemed tolerable enough for Travis to do it again.