Assuming a Named Graph with the following triples:

...
<http://linkedgeodata.org/triplify/node454640663> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://linkedgeodata.org/ontology/hostel> .
<http://linkedgeodata.org/triplify/node454640663> <http://www.georss.org/georss/point> "53.2752338 -9.0443748" .
<http://linkedgeodata.org/triplify/node454640663> <http://www.w3.org/2003/01/geo/wgs84_pos#long> "-9.0443748"^^<http://www.w3.org/2001/XMLSchema#decimal> .
<http://linkedgeodata.org/triplify/node454640663> <http://www.w3.org/2003/01/geo/wgs84_pos#lat> "53.2752338"^^<http://www.w3.org/2001/XMLSchema#decimal> .

<http://linkedgeodata.org/triplify/node280886720> <http://www.w3.org/2000/01/rdf-schema#label> "Abbey House" .
<http://linkedgeodata.org/triplify/node280886720> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://linkedgeodata.org/ontology/bed_and_breakfast> .
<http://linkedgeodata.org/triplify/node280886720> <http://www.georss.org/georss/point> "53.2874983 -9.0702631" .
<http://linkedgeodata.org/triplify/node280886720> <http://www.w3.org/2003/01/geo/wgs84_pos#long> "-9.0702631"^^<http://www.w3.org/2001/XMLSchema#decimal> .
<http://linkedgeodata.org/triplify/node280886720> <http://www.w3.org/2003/01/geo/wgs84_pos#lat> "53.2874983"^^<http://www.w3.org/2001/XMLSchema#decimal> .
...

In order to convert these triples ( with geo properties ) to geometries to use spartial query, you need to run the DB.DBA.RDF_GEO_FILL () function to populate the special RDF_GEO table with the point information as detailed at Creating Geometries From RDF Data documentation section.

Then the geo-spatail information will be available and can be queried.

Note: RDF_GEO and associated indexes are created when the database is first created and thus just needs to be populated with the geometry data in the RDF triples, which is what the DB.DBA.RDF_GEO_FILL () function does.