The water tower of Rijswijk has been realized in 1911, by architect N. Biezeveld. The height of the tower is 30 meters. In the top of the tower the basin is located. The basin contains 200m3 of water. The new function of this listed building is a private house. To react on the industrial characteristics of the tower, mostly rough materials have been used to create the new interior. The open space on ground level is divided in two layers: sleeping and bathing has been located on the new level 1, while living is done on ground level. The level 1 can be reached by an industrial looking aluminum stairs in the new vertical glass core. The new glass core accentuates the vertical round stairs in the middle of the space: this juxtaposition makes the stairs appear as an artefact. In the skin of the concrete water tower two vertical openings have been made in order to receive daylight in the interior. The new openings are contrasting in measurements and detailing to the existing openings.