junto a and al lado de are again one of the prepositions with alternative counterparts, meaning next to, beside, at the side of

Junto a la casa había un arbol. = Next to the house was a tree. alternatively: Al lado de la casa había un arbol. = Next to the house was a tree. Luchó junto a Bolívar por la independencia de latinoamérica. = He fought beside Bolivar for the independency of Latin America. alternatively: Luchó al lado de Bolívar por la independencia de latinoamérica. = He fought at the side of Bolivar for the independency of Latin America.