Yes there are. Here's a picture of one:

as if they still lived in tents.

The only Christian churches (*defined as "a community of Christians" not "a church building") in North Korea are either underground churches or expat churches in foreign enclaves. Under the communist regime in North Korea, all religion is prohibited and deemed threatening to the security of the state. As a result of this policy, Christians in the region must worship secretly and in constant fear. Many are caught and punishments range from fines to imprisonment to torture and even execution. Others take a potentially greater risk and flee to neighboring China, where, if caught, repatriation followed by execution is almost a certainty. Unfortunately, China is proving its reputation for religious intolerance, and consequently its lack of acknowledgement of human rights, and is forcing repatriation for many who cross its borders seeking asylum from North Korea. A former North Korean State Security Agency official has given evidence that North Koreans who try to escape to a third country are usually executed upon their return. And yet the deportations continue, in clear breach of China's obligations under the 1951 UN Refugee Convention. Sadly, it would seem that China is not interested in being questioned on its actions in these matters, and has been moving exceptionally quickly in repatriating the captured North Koreans. According to the US Commission on International Religious Freedom, "between 30,000 and 300,000 North Koreans are now in China. Most have fled to escape the dire conditions in North Korea, including the denial of religious freedom and all other basic human rights in that country... The Chinese government does not grant refugee status to fleeing North Koreans, even though most if not all meet the international criteria for that status. In addition, the Chinese government does not allow the UNHCR to operate in the border region between China and North Korea, thus preventing that organization from interviewing those crossing the border and assessing their status as refugees."

They are there only for show. They open usually for visiting dignitaries so the government can claim they are being religiously tolerant but almost all of them stay closed all year long. A few that open have services whee people must also 'worship' or show appreciation for their "Dear Leader", as Kim is known as. Most of the churches are state approved Protestant churches.

Yes there are churches in North Korea. There are state created church buildings in Pyongyang such as the protestant Pongsu Church and the Chilgol Protestant Church. Also there is the Changchung Catholic Cathedral. Recently Kim Jong Il had constructed Russian Orthodox Church of Life-Giving Trinity in the Chonbek. All of these church buildings are considered for show only and do not function as non Koreans know a church. According to people who have defected to the South there are underground churches that are not state-sanctioned and meet in secret.