Situated at the highest part of the town square, overlooking the urban area, the visitor can see the remains of the palace that was once the residence of Zerain's noble family.
The palace's most characteristic features are the three walls that once surrounded the house-tower. The building also contains a gothic archway, over which the following inscription runs from left to right: 'Holy Mary, full of grace, bless us'.
Above this archway the visitor can also see the town's oldest coat of arms, along with an image whose meaning has never been deciphered: 'A dull sun enfolded in a quarter moon and surrounded by four, eight-point stars'. Although these stone-carved images have been worn down over the centuries, Zerain Palace remains firm, displaying its greatness and nobility with pride.
The earliest written reference to the palace dates back to 1364, and despite extensive modifications, it still retains the same aura of nobility as the original house-tower.
The palace that we see today is the product of the 15th century conflict between two warring bands, the Gamboínos and the Oñacinos, since, as a result of this struggle, in 1457 King Henry IV ordered the top of the tower to be chopped off. The tower was later rebuilt.
However, even this did not destroy the house-tower's strength and nobility, despite the fact that this was precisely its objective. Centuries later, the people of Zerain continue to acknowledge the building and admire it as the palace it undoubtedly is.