Indan Sax Sonig Hot

Given common travel or social media captions, the user likely meant:

"This city is beautifully interesting"
or
"Such a beautiful, interesting city"

Pros:

Cons:

However, the phrase as written is non-standard and likely a misspelling or phonetic attempt. The closest natural Mongolian phrase would be: indan sax sonig hot

"Энэ сайхан сонирхолтой хот" (Ene saikhan sonirkholtoy khot)
"This beautiful, interesting city"

Or possibly:

"Индан сайхан сониг хот" — which is grammatically broken, but might mean "For this, a beautiful news city" (unlikely).