What is the massive red building in Pettah market.

That magnificent structure is the Jami Ul Alfar Mosque universally known as the Red Mosque. It is one of the most stunning and famous architectural landmarks in Colombo featuring incredible candy cane striped brickwork. Yes tourists are warmly welcomed to visit the inner courtyard and admire the architecture provided you avoid visiting during the main Friday prayer times. You must dress very conservatively ensuring your arms and legs are completely covered and women will be provided a cloak to wear over their clothes before entering the sacred space.