A group of Guantanamo Bay detainees on Thursday became the first to enter a new maximum-security prison — a $37 million facility designed to restrict contact among the prisoners and prevent attacks on guards.

A total of 42 detainees were brought to the prison perched on a plateau overlooking the Caribbean Sea from another maximum-security camp at the U.S. naval base in eastern Cuba, said Navy Cmdr. Robert Durand.

The 178-cell prison, constructed beside another modern maximum-security facility built in 2004, will allow the U.S. naval base to close Camp 3, which was constructed in 2002 with walls of thick-gauge, chain-link metal, Durand said.

U.N. human rights investigators and foreign governments have called on the U.S. government to close the entire detention center. But Guantanamo officials say they have no choice in dealing with men deemed enemy combatants during the war on terrorism.

The concrete-and-steel jailhouse was originally designed as a medium-security facility. But the military made several modifications to Camp 6, citing concerns raised by three suicides in June and a clash in May between guards and detainees armed with makeshift weapons.

Detainees confined in individual cells will look out through long, narrow windows on areas with metal tables and stools that were meant as shared living spaces but will now be off-limits. An open-air recreation area has been divided into smaller spaces, which will hold only one detainee at a time.

Shower doors were redesigned to allow guards to shackle prisoners' hands and feet before they leave the stalls, and "anti-jump fencing" was installed on second-tier catwalks as part of the modifications.

The prison includes air conditioning, an onsite medical center, and two rooms that will allow them to meet privately with their lawyers, Durand said.

"The new, climate-controlled camp is designed to improve quality of life for both detainees and the guard force," he said.

U.S. Navy Cmdr. Kris Winter said the modifications will help make guards safer. In the last year and a half, the military has recorded more than 430 assaults by detainees using "cocktails" of bodily excretions thrown at guards and 225 physical assaults.

"As a commander, I don't like my folks being in danger every day," Winter said this week while leading journalists on a tour of the prison.

By limiting the detainees' interaction, Guantanamo officials said the design also aims to reduce their ability to communicate. Navy Rear Adm. Harry Harris, commander of the jail, has described the June 10 suicides in Camp 1 as a coordinated protest — "not an act of desperation but an act of asymmetric warfare against us."

The May 18 ambush inside Camp 4 — the prison reserved for the most compliant prisoners — resulted from a plot hatched by detainees as word spread that guards were searching cells for contraband medication following two suicide attempts, officials said.

To allow each cell block's prayer leader to be heard, guards will open the "beanhole" slot on his door during prayers five times a day. The others' doors will remain sealed, Navy Cmdr. Kris Winter said.