I've raced Mallorca 70.3 three years running and it never fails to disappoint. It's easy and cheap to get to, the weather is always amazing, and what's not to love about racing adjacent to pure white sand and crystal clear sea?
The sea swim is crystal clear and because it's in a bay rarely choppy. The climb on the bike is awesome, it's sustained but doable and the views are really spectacular. The second part of the course is fast and flat (often windy though) and slightly less scenic. The run extends along the beach front and competitors benefit from some decent spectator support here. The run is usually pretty hot but you can cool off in the sea afterwards which is a massive bonus!
Being the largest 70.3 in the world it's not necessarily a top choice for qualifying slots of podium positions but it's a great season opener and one of the most fantastic race locations on the European circuit.