Sei bella! in the singular and Siete belle! in the plural are Italian equivalents of the English phrase "You are beautiful!" The personal pronouns tu (informal singular "you") and voi (informal plural "you all") need not be used other than for emphasis since context and verb endings make the statement's focus clear. The respective pronunciations will be "SEH-ee BEL-la" in the singular and "SYEY-tey BEL-ley" in the plural in Italian.
"You are beautiful!" in English is Sei bella to a female and Sei bello to a male in Italian.
"Beautiful horse" in English is bel cavallo in Italian.
"Beautiful woodland!" in English is Bel bosco! in Italian.
"Beautiful walls!" in English is Bellissime mura! in Italian.
"Beautiful mountains!" in English is Belle montagne! in Italian.
"Beautiful night" in English is bella notte in Italian.
"Beautiful moments!" in English is Bei momenti! in Italian.
"Beautiful mommy!" in English is Bella mamma! in Italian.
"Beautiful disaster" in English is bel disastro in Italian.
"Beautiful nephew" in English is bel nipote in Italian.
"We are very beautiful!" in English is Siamo bellissime!in Italian.
"Beautiful dream" in English is bel sogno in Italian.
"Beautiful Rome!" in English is Bella Roma! in Italian.