Tsipras-Mitsotakis attend a joint dinner (pics)
The dinner is held in honor of UN Secretary General Ban Ki-moon
Ban Ki-moon visits Solidarity Athens Centre
"Instead of building walls we need to build bridges between people," he said
Ban Ki-moon to attend dinner with Pavlopoulos, Tsipras, Mitsotakis
He will also visit Lesvos to meet with refugees, migrants and volunteers