Search infomation about a domain:

hostname:<domain>

In browser search bar:

<https://www.shodan.io/domain/><domain>

Search an open port in a specific city:

port:502 country:"IT" city:"Pippocity"

Shodan indexes SSL certificates then you can find hosts that have certificate bindend to domain.com or subdomains:

ssl:"domain.com"
ssl:"*.domain.com"
ssl.cert.subject.CN:"domain.com"
ssl.cert.subject.CN:"*.domain.com"
ssl.cert.subject.alt_name:"domain.com"
ssl.cert.subject.alt_name:"*.domain.com"
ssl.cert.fingerprint:<SHA1_HASH_CERTIFICATE>