Human Tower
Castellers de Vilafranca start to form a human tower called castell during a biannual competition in Tarragona city, Spain.Reuters

An amazing set of photos released show thousands of people flocking together to create human towers. Formally, the competition is addressed as Concurs de Castells, which is a biennial event of Tarragona, Spain.

In this sport, teams, each comprising 500 members or more, compete with each other at building the tallest human tower, which may or may not go up to as many as eight tiers. Participants on the heavier side build the foundation by staying on the ground, while the light-weighted ones climb the humans to make formations.

It is an integral part of the Catalan culture and over 20,000 people visit the arena to watch the spectacle. It is listed in UNESCO's cultural heritage list.