Merkslas is located in the Northern Kempen region, some 40 km from Antwerp.
The area, which is  rich in ponds and moors, is watered by the Scheldt and Maas rivers.  

In the open meadows of Koekhoven village, near the peaty bogs of Turnhout, the Mark river rises  and meanders northwesterly towards the Belgo-Dutch frontier.  Merksplas actually derives its name from the Mark river and the Dutch word plas, meaning pond. 

During medieval times, people traveling to Merksplas had to go wading and splashing through ponds and bogs.  The inhabitants of Merksplas were thus nicknamed spetsers (literally meaning "splashers"), and the town is known as the spetserdorp  or the "village of splashers".  This historical fact is aptly commemorated by a fountain called De Spetser in the market square of Merksplas. 

The oldest mention of Merksplas (previously written Marcblas) appears in a document dated 1148 confirming the transfer of the village church to the Norbertine monks, who ran it for six centuries. The domain of Merksplas later belonged either to the County of Turnhout or to the County of Hoogstraten. In the Middle Ages, Merksplas was a popular place of pilgrimage where St. Roch was invoked against the black plague.

Today Merksplas is mostly known for its prison, which was opened in 1822 as a refuge for beggars. The refuge evolved into a State charity house for vagabonds, and then into a detention centre for illegal immigrants.  The prison lies within a domain covering 15,000 acres.  The area, known as Merksplas Colony, is surrounded by a circulary canal.  Merksplas Colony was designed according to a grid pattern including open fields, pastures, pine and beech woods, moors and remains of peat bogs as well as a few clay pits, which are used today as storing places or fish ponds. 

Since 1999, Merksplas Colony has been officially protected by Belgian law as a national heritage site. The five main buildings of the domain are the prison, the center for illegal immigrants, the Great Farm, the former school and the prison's chapel, which is today used as the visitor's center with the Museum of the Loss of Liberty.