Trump spoke about the visit to Greta Van Susteren on Fox News.
"President Obama went to a mosque today in Baltimore to talk about religious tolerance and to talk about the contributions Muslims have made in the United States," Greta said. "Your thoughts about that?"
"I don't have much thought. I think that you can got to lots of places," Trump said. "I don't know, maybe he feels comfortable there."
He continued: "We have a lot of problems in this country, Greta. There are a lot of places you can go, and he chose a mosque. That's his decision, that's fine."
While at the mosque, Obama spoke about the contributions that Muslims have made to America and even alluded to Trump.
"Inexcusable political rhetoric against Muslims that has no place in our country," Obama said. "It's no surprise then that threats against Muslims have surged."
Obama added: "We can't be bystanders to bigotry. Together, we've got to show that America truly protects all faiths. As we protect our country from terrorism, we should not reinforce the ideas and the rhetoric of the terrorists themselves."