The mayor will solemnize their wedding ceremony at the town hall.

solemnize 是动词，由形容词 solemn（庄严的、隆重的）加上动词后缀 -ize 构成，意思是"使...庄严化"，引申为"正式举行（婚礼等仪式）"或"主持（仪式）"。