The construction works of Viru prison, which covers 16 hectares in the Estonian town Jõhvi, occupied over 2,700 people. At the peak period of construction, there were over 600 people working at the site. Contracts were signed with more than 220 sub-contracting companies. What makes Viru Prison different from other Estonian prisons are the buildings that are connected with one another by galleries, which enable the prison to keep the imprisoned in closed rooms within the whole period of detention. For Merko Ehitus, the main challenge of the whole project was the security and the complicated logistics arising from the security requirements. The construction works of Viru prison started in August 2006. The prison is surrounded by nearly six kilometres of external peripheries; prisoners are separated from the rest of the world by two metal and one concrete periphery, which are additionally secured by electronic surveillance. Viru prison has cells for 1000 prisoners, administrative rooms, a school, a church, a sports building, a library, workshops and rooms for social work. The prison employs altogether 340 people.