Born Caspar (Kaspar) van Baerle in Antwerp, Barlaeus' parents fled the city when it was occupied by Spanish troops shortly after his birth.

In 1647, he wrote an account of the Dutch colonial empire in Brazil, inspired by the leadership of John Maurice of Nassau (Johan Maurits) at Recife.

In 1638, Barlaeus wrote Medicea Hospes, sive descriptio publicae gratulationis, qua ... Mariam de Medicis, excepit senatus populusque Amstelodamensis.

Published by Willem Blaeu, it includes two large folding engraved views of the ceremonies on the occasion of the French queen mother Marie de Medici's triumphal entry into Amsterdam in 1638.

Marie de Medici actually traveled to the Netherlands as exile, but spectacular displays and water pageants took place in the city's harbor in celebration of her visit.

There was a procession led by two mounted trumpeters; a large temporary structure erected on an artificial island in the Amstel River was built especially for the festival.