光有3种常用意思： 1. n. Light. example: 光太亮了，我的眼睛很疼。 2. adv. Just. example: 光是想想都觉得很可怕。just think about it makes me scared. 3. adv. all gone. example: 我花光了所有的钱。I spent all the money.

here 光 means only. e.g. 她光笑不说话。 Tā guāng xiào bù shuōhuà. She just smiled and said nothing

may be it means only or just

Used to emphasize that one aspect alone is enough to cause another action or result.

光 here means simply or just. It emphasizes that you don't have do anything else, simply walking on the street can make you feel how welcoming the city is. Hope it helps.