A Muslim is permitted to enter Churches and other houses of worship. There is reference to that in the acts of some of the Prophet's Companions (may Allah be pleased with them all). The issue, by and large, depends on the intention of the person doing that. If the intention is to receive blessings from or confess sins to anyone other than Allah, then such a visit is surely prohibited. If, on the other hand, the purpose is just to familiarize oneself with how Christians conduct their services, or to share in a happy occasion such as a wedding, then this is surely permissible.
Responding to the question, Sheikh Ahmad Kutty, a senior lecturer and Islamic scholar at the Islamic Institute of Toronto, Ontario, Canada, states the following:
"It all depends on the intention and purpose of your visit. If you are entering the Church for the purpose of worship or receiving blessings or confessing your sins or beseeching favors from other than Allah, then you are wrong.
If, on the contrary, it is not for any of the above reasons, and you simply went there to observe how the Christians conduct their services and familiarize yourself with their ways or for the purpose of outreach, dialogue, cooperation in virtuous acts, etc., then there is nothing wrong with that.
In such cases, it may even be highly recommended depending on the nature of your visit and the circumstances. We know that the Caliph `Umar (may Allah be pleased with him), while in Jerusalem, was taken around in the ancient Church by the patriarch, but he refused to pray inside; when asked about it he said, "I am afraid, if I were to do so, Muslims might later claim it as a prayer place or a musalla.
To conclude, I can say that there is nothing wrong for Muslims in visiting churches or synagogues or temples if the purpose is other than worship or religious reasons. May Allah help us all to remain steadfast on the straight path and guide our steps."