yeah, the geohash is listed in the event in a 'g' tag. I think its defined in NIP-52 https://github.com/nostr-protocol/nips/blob/master/52.md
If you "View Raw" on one of the events you can see it has a bunch of 'g' tags
Discussion
Could prove to be really useful for advertising services that accept Bitcoin... Or for nostr:nprofile1qqs2xugc5jyguqkj36rk0syv4tmnkjdtmtperttl7x9rqjy3ustdcvcpz3mhxue69uhhyetvv9ujuerpd46hxtnfduqs6amnwvaz7tmwdaejumr0dsq3camnwvaz7tmjv4kxz7fwd46hg6tw09mkzmrvv46zucm0d5yx7efd
Working on rolling out geohash support #soon™!