geography - Devoted to high culture

_{This puzzle is part 4 of Gladys' journey across the globe. Each part can be solved independently. Nevertheless, if you are new to the series, feel free to start at the beginning: Introducing Gladys.}

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Dear Puzzling,

Today I visited a rather unusual religious site. The people here seem highly spiritual, yet at the same time extremely tolerant. Unfortunately I was not allowed to witness their ceremonies myself, but I did get to take a tour of the church during the day.

Wish you were here!
Love, Gladys.

Across
1. From the creators of Ice Age | Unpaid trainee
2. Irish singer | Joker actor
3. Small image | Gemstone
4. Politician who would be sober tomorrow
5. Ballad's Chevy | English county
6. Couch | Piece of artillery

7. Frantic | Stitch up
8. Mediterranean island | Funeral container

Down
1. German empire | Fantasy monster
2. 2.54 centimetres | Ethiopian language
3. Happy | Japanese politician
4. Author Fleming | Repeat aloud
5. Open with a key | City with its own gulf
6. Name spelt with PH instead of V | Signified by Σ
7. Basque separatists | Central, interior

8. Small bread | Urban area

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_{Gladys will return in "Gladys spins the wheel".}

Answer

Gladys is at

the INTERNATIONAL CHURCH OF CANNABIS (yes, that's a real thing) in Denver, CO

The gray numbers

are meant to be interpreted as a gridless Slitherlink where blanks are considered 0. The solution to this Slitherlink encloses some of the letters of the crossword, which when read from top to bottom and left to right give us Gladys's location.

Completed grid:

Additionally, the answer is confirmed by

the title mentioning "high" culture and the letter in the flavortext saying that the people there are spiritual but tolerant.