Complex sentence: During the second half of the 1960s, as happened along the rest of the Costa Blanca, there was a tremendous boom in construction in Calp because of political change and the emergence of tourism as a phenomenon of the masses.
Split into simpler sentences: During the second half of the 1960s, as happened along the rest of the Costa Blanca, there was a tremendous boom in construction in Calp. This was due to political change and the emergence of tourism as a phenomenon of the masses.